Thanks for the question! This'll take time to make a good tutorial. I hope to have it done today. It's a good idea. I had actually made a free plugin for my site and another friend which allows featuring sites to cross promote, similar to what you want to do. But, for the tutorial, I'll just write how to manually do it.

I'll have to come back to this for you. There is a bug stripping the html from the block that I'm need to show in the tutorial. Sorry!

Okay, here ya go! It's pretty detailed and has code examples in it. If you want it to look different than that, you can play with Bootstrap codes to insert those instead of what I used. Here's the tutorial for you to try:

Make a page to feature other sites or content