Hey James, thank you so much!
For the featured articles, I added a field to the frontmatter in my markdown files called isFeatured. When I want to grab my featured articles, I check the frontmatter of each post and filter out the ones that aren't featured. From that list, I just grab the top three tops!
I linked the repo in the article for you to look at. If you look at how each article is structured, you'll see that field in the frontmatter. Then if you head into utils/mdxUtils.ts, you'll find a function called getPopularPosts. This is where that filtering logic is.
Happy coding!