So ...

Let's see the HOW part ...

This time I am going to use a plugin called Inline Related Posts.

Here it is:

https://wordpress.org/plugins/intelly-related-posts/

It's a quite big plugin (1.5 MB), so let's see the usual speed tests ...

Here are my results before installing the plugin ...

... and the result after installing and activating the plugin:

As you can see, it's a big plugin, but is definitely a well-coded one.

Now, let's see how it works ...