Portfolio of layout designer in GitHub. How to make it beautiful?

Question

GitHub

As you know, GitHub can be used as hosting for your site. I am engaged in layout and I had an idea to implement something like a small portfolio. On the main page - a grid with preview blocks. When you click on a block, a specific project opens, namely a static html page. Thus, it would be possible to visually evaluate the layout or, more simply, "poke".
I created a repository, threw a couple of folders with projects and a simple index.html into the root, in which links (of this plan: href = "name of the folder with the project") to these projects are registered. The main index.html and project folders are at the same level in the repository. The main page opens, but when you click on the block preview, you get a 404 error and a link to the GitHub Pages documentation. No matter how much I read it, alas, nothing good comes out. I tried to google, but I can't figure it out.
If someone came across, tell me, please.

Answer 1

href="/folder/"
https://help.github.com/articles/creating-project-...

Answer 2

There was also a similar question, before the link you need to put two dots