Create your own author bio box in WordPress without a plugin.

I have tested the following author box in TwentySixteen Child theme and Genesis Child themes as well as some random themes.
The final result using Fontawesome icons. One can switch them out with other icons.

Custom Authorbox

The Users -> Your profile contact info only has a very few fields such as Email and Website.

We will be adding (as can be seen below) Facebook, Twitter, LinkedIn, Youtube, Github, Google+ and Pinterest.
By following the examples in the code it becomes fairly easy to also add additional social media profiles.

Users -> Your Profile I have added additional contact info.

In your child theme functions.php file add the following code:

/* Add Contact Methods in the User Profile - https://codex.wordpress.org/Plugin_API/Filter_Reference/user_contactmethods */

function add_user_contact_methods( $user_contact ) {
 $user_contact['facebook'] = __( 'Facebook URL' );
 $user_contact['skype'] = __( 'Skype Username' );
 $user_contact['twitter'] = __( 'Twitter Handle' );
 $user_contact['youtube'] = __( 'Youtube Channel' );
 $user_contact['linkedin'] = __( 'LinkedIn' );
 $user_contact['googleplus'] = __( 'Google +' );
 $user_contact['pinterest'] = __( 'Pinterest' );
 $user_contact['instagram'] = __( 'Instagram' );
 $user_contact['github'] = __( 'Github profile' ); 
 return $user_contact; 
}
add_filter( 'user_contactmethods', 'add_user_contact_methods' );


//Load Fontawesome
function themeprefix_fontawesome_styles() {
 wp_register_style( 'fontawesome' , 'https://maxcdn.bootstrapcdn.com/font-awesome/4.6.3/css/font-awesome.min.css', '' , '4.4.0', 'all' );
 wp_enqueue_style( 'fontawesome' );
}
add_action( 'wp_enqueue_scripts', 'themeprefix_fontawesome_styles' ); 


function wpb_author_info_box( $content ) {

global $post;

// Detect if it is a single post with a post author
if ( is_single() && isset( $post->post_author ) ) {

// Get author's display name - NB! changed display_name to first_name. Error in code.
$display_name = get_the_author_meta( 'first_name', $post->post_author );

// If display name is not available then use nickname as display name
if ( empty( $display_name ) )
$display_name = get_the_author_meta( 'nickname', $post->post_author );

// Get author's biographical information or description
$user_description = get_the_author_meta( 'user_description', $post->post_author );

// Get author's website URL 
$user_website = get_the_author_meta('url', $post->post_author);

// Get author's email
$user_email = get_the_author_meta('email', $post->post_author);

// Get author's Facebook
$user_facebook = get_the_author_meta('facebook', $post->post_author);

// Get author's Skype
$user_skype = get_the_author_meta('skype', $post->post_author);

// Get author's Twitter
$user_twitter = get_the_author_meta('twitter', $post->post_author);

// Get author's LinkedIn 
$user_linkedin = get_the_author_meta('linkedin', $post->post_author);
 
// Get author's Youtube
$user_youtube = get_the_author_meta('youtube', $post->post_author);

// Get author's Google+
$user_googleplus = get_the_author_meta('googleplus', $post->post_author);

// Get author's Pinterest
$user_pinterest = get_the_author_meta('pinterest', $post->post_author);

// Get author's Instagram
$user_instagram = get_the_author_meta('instagram', $post->post_author);
// Get author's Github
$user_github = get_the_author_meta('github', $post->post_author);


// Get link to the author archive page
$user_posts = get_author_posts_url( get_the_author_meta( 'ID' , $post->post_author));
if ( ! empty( $display_name ) )
$author_details = '<p class="author_name">About ' . $display_name . '</p>';

// Author avatar - - the number 90 is the px size of the image.
$author_details .= '<p class="author_image">' . get_avatar( get_the_author_meta('ID') , 90 ) . '</p>';
$author_details .= '<p class="author_bio">' . get_the_author_meta( 'description' ). '</p>';
$author_details .= '<p class="author_links"><a href="'. $user_posts .'">View all posts by ' . $display_name . '</a></p>'; 

// Display

// Check if author has a website in their profile
if ( ! empty( $user_website ) ) {
// Display author website link
$author_details .= '<a href="' . $user_website .'" target="_blank" rel="nofollow" >Website</a></p>';
} else { 
// if there is no author website link then just close the paragraph
$author_details .= '</p>';
}


// Fontawesome icons: https://fontawesome.io/icons/

// Display author Email link
$author_details .= ' <a href="mailto:' . $user_email .'" target="_blank" rel="nofollow" title="E-mail" class="tooltip"><i class="fa fa-envelope-square fa-2x"></i> </a></p>';


// Check if author has Facebook in their profile
if ( ! empty( $user_facebook ) ) {
// Display author Facebook link
$author_details .= ' <a href="' . $user_facebook .'" target="_blank" rel="nofollow" title="Facebook" class="tooltip"><i class="fa fa-facebook-official fa-2x"></i> </a></p>';
} else { 
// if there is no author Facebook link then just close the paragraph
$author_details .= '</p>';
}

// Check if author has Skype in their profile
if ( ! empty( $user_skype ) ) {
// Display author Skype link
$author_details .= ' <a href="' . $user_skype .'" target="_blank" rel="nofollow" title="Username paaljoachim Skype" class="tooltip"><i class="fa fa-skype fa-2x"></i> </a></p>';
} else { 
// if there is no author Skype link then just close the paragraph
$author_details .= '</p>';
}

// Check if author has Twitter in their profile
if ( ! empty( $user_twitter ) ) {
// Display author Twitter link
$author_details .= ' <a href="' . $user_twitter .'" target="_blank" rel="nofollow" title="Twitter" class="tooltip"><i class="fa fa-twitter-square fa-2x"></i> </a></p>';
} else { 
// if there is no author Twitter link then just close the paragraph
$author_details .= '</p>';
}

// Check if author has LinkedIn in their profile
if ( ! empty( $user_linkedin ) ) {
// Display author LinkedIn link
$author_details .= ' <a href="' . $user_linkedin .'" target="_blank" rel="nofollow" title="LinkedIn" class="tooltip"><i class="fa fa-linkedin-square fa-2x"></i> </a></p>';
} else { 
// if there is no author LinkedIn link then just close the paragraph
$author_details .= '</p>';
}

// Check if author has Youtube in their profile
if ( ! empty( $user_youtube ) ) {
// Display author Youtube link
$author_details .= ' <a href="' . $user_youtube .'" target="_blank" rel="nofollow" title="Youtube" class="tooltip"><i class="fa fa-youtube-square fa-2x"></i> </a></p>';
} else { 
// if there is no author Youtube link then just close the paragraph
$author_details .= '</p>';
}

// Check if author has Google+ in their profile
if ( ! empty( $user_googleplus ) ) {
// Display author Google + link
$author_details .= ' <a href="' . $user_googleplus .'" target="_blank" rel="nofollow" title="Google+" class="tooltip"><i class="fa fa-google-plus-square fa-2x"></i> </a></p>';
} else { 
// if there is no author Google+ link then just close the paragraph
$author_details .= '</p>';
}

// Check if author has Pinterest in their profile
if ( ! empty( $user_pinterest ) ) {
// Display author Pinterest link
$author_details .= ' <a href="' . $user_pinterest .'" target="_blank" rel="nofollow" title="Pinterest" class="tooltip"><i class="fa fa-pinterest-square fa-2x"></i> </a></p>';
} else { 
// if there is no author Pinterest link then just close the paragraph
$author_details .= '</p>';
}

// Check if author has Github in their profile
if ( ! empty( $user_github ) ) {
// Display author Github link
$author_details .= ' <a href="' . $user_github .'" target="_blank" rel="nofollow" title="Github" class="tooltip"><i class="fa fa-github-square fa-2x"></i> </a></p>';
} else { 
// if there is no author Github link then just close the paragraph
$author_details .= '</p>';
}

// Pass all this info to post content 
$content = $content . '<footer class="author_bio_section" >' . $author_details . '</footer>';
}
return $content;
}

// Add our function to the post content filter 
add_action( 'the_content', 'wpb_author_info_box' );

// Allow HTML in author bio section 
remove_filter('pre_user_description', 'wp_filter_kses');

NB! I noticed some themes had a problem with the included tooltip class in the above code. If you can not see the icons in the author box using your theme then go into the code and remove all mention of the tooltip class for the icons to show.

Adding a tooltip

In the above code I have added a class called tooltip. – class=”tooltip”
On hover the tool tip shows the title of the icon. I have also added a title for each link. Such as title=”E-mail”
Below you can see what the tooltip I made looks like.

Custom Author bio box Hover tooltip

Adding the CSS

Add the following CSS  to your style.css (or any stylesheet):

/* Hide default author box - If this is not included TwentySixteen will atleast have two author boxes. Check with the theme your using. */
.author-info {
 display: none;
}

/* The new author box */
.author_bio_section{
 background: none repeat scroll 0 0 #F5F5F5;
 padding: 15px 12px 45px 23px;
 border: 1px solid #ccc;
 box-shadow: 0px 3px 3px #444;
}

.author_bio_section a{
 text-decoration: none;
 box-shadow: none !important; 
}

.author_bio_section a:hover{
 color: red; 
}

/* About and author name or nick */
.author_name{
 font-size:16px;
}

/* Surrounding avatar image */
.author_image {
 float: left;
 margin: 0 15px 0 0;
 background: red;
 
 border-radius: 5px !important;
 border: 1px solid #ccc;
 box-shadow: 0px 1px 1px #ccc;
}

/* avatar image */
.avatar {
 border-radius: 5px !important;
}


/* View all posts by and website link */
.author_links {
 margin: 0;
 float: left;
 padding: 0 20px 0 0;
}

/* Fontawesome icon */
.fa {
 padding: 5px 10px 5px 9px;
 margin: -10px 10px 0 0;
 float: left;
 background: #205D7A;
 color: #fff;
 border-radius: 5px;
 transition-property: opacity;
 transition-delay: 0.3s;
 transition-duration: .5s; 
 border: 1px solid #333;
}

/* Fontawesome icon */
.fa:hover {
 background: #005781;
 color: #fa7777; 
 border: 1.5px solid #333;
}


/* --- Tooltip --- */

/* black up arrow */
.tooltip:hover:before{
 border: solid;
 border-color: #005781 transparent; // Arrow
 border-width: 0 7px 7px 7px; // Arrow
 top: 35px;
 content: "";
 left: 40%;
 position: absolute;
 z-index: 99; 
 opacity: .8;
}

/* black tool tip title box */
.tooltip {
 display: inline;
 position: relative;
 right: 8%;
 
}

/* black tool tip title box */
.tooltip:hover:after{
 background: #005781;
 background: rgba(32,93,122, .9);
 border-radius: 5px;
 top: 40px;
 color: #fff;
 content: attr(title);
 left: 40%;
 padding: 5px 8px;
 position: absolute;
 z-index: 98;
 width: 110px;
}

Adding Media Queries

I began looking at this and noticed that if someone fills out all the social media links there will be a lot of buttons. Making the browser window smaller some icons will jump to line 2. The tooltip will then not look pretty. Here are some media queries adjustments that I made. I initially tested with the child theme Twenty Sixteen and then a Genesis child theme. So that these should look alright there. But you will need to readjust to fit your own theme.
Add the following to your own CSS file.

@media only screen and (max-width: 1250px) {
 .fa {
 padding: 4px;
 margin: -10px 10px 0 -2px;
 background: red; // For testing purpose
 }

}

@media only screen and (max-width: 1150px) {
 .fa {
 padding: 3px;
 margin: -10px 10px 0 -7px;
 background: green; // For testing purpose
 }

}

@media only screen and (max-width: 510px) {
 .fa {
 padding: 1px;
 margin: -10px 10px 0 -11px;
 background: blue; // For testing purpose
 }

}

It also gives an idea of how Media Queries work. Remember to after your finished testing to remove the background colors.

Using your own social media icons

This part is little more tricky.

An example with using the above Facebook code:
$author_details .= ‘ <a href=”‘ . $user_facebook .'” target=”_blank” rel=”nofollow” title=”Facebook” class=”tooltip”><i class=”fa fa-facebook-official fa-2x”></i> </a></p>’;

Replace with something like:
$author_details .= ‘ <a href=”‘ . $user_facebook .'” target=”_blank” rel=”nofollow” title=”Facebook” class=”tooltip”><img src=”‘ . plugins_url( ‘/images/facebook-icon.png’, dirname(__FILE__) ) . ‘” width=”45″ class=”social-icons”> </a></p>’;

The reason why I added the dirname(__FILE__) ) is that I am placing the code into a my most used custom functions plugin I will later on add to my Github repository (I will write about it). If your using the author box in your theme just skip the dirname(__FILE__) ).

Then create the CSS class name social-icons. Such as
.social-icons {
some code.
}

https://codex.wordpress.org/Function_Reference/plugins_url

Some additional information.

I made a custom.css stylesheet which I added in the root of the child theme folder.
I also placed the code that I had entered into the functions.php file into another php file.
Placing php and CSS into their own external files one needs to call them into the functions.php so they are used.
Here is the code I put into the functions.php file:

// INCLUDE - external php pages.
include_once( get_stylesheet_directory() . '/lib/code-snippets.php' ); // Various code snippets.

//Another way: include_once( 'lib/code-snippets.php' );


// Add custom CSS stylesheets 
add_action( 'wp_enqueue_scripts', 'load_custom_style_sheet' );
function load_custom_style_sheet() {
wp_enqueue_style( 'custom-stylesheet', CHILD_URL . '/custom.css', array(), 1.0 ); 
}

If you instead want to try out a plugin

wordpress.org/plugins/wp-author-box-lite/
wordpress.org/plugins/simple-author-box/
wordpress.org/plugins/fancier-author-box/

Resources

https://www.wpbeginner.com/wp-tutorials/how-to-add-an-author-info-box-in-wordpress-posts/
and wpbeaches.com/author-box-genesis/

Modified from Neil Gowrans wpbeaches.com/author-box-genesis/ tutorial.
I have also borrowed some code from a tutorial from Andor Nagy.
The tooltip CSS code came from webdesignerdepot.com/2012/11/how-to-create-a-simple-css3-tooltip/

Fontawesome icons
Newest version of Fontawesome icons are located here: https://www.bootstrapcdn.com/fontawesome/