Guidance/help for creating WordPress theme

I have a responsive theme created with html/css. I thought it would be a good project to turn it into a WordPress theme. I have been doing some research in the WordPress codex and such and have a decent understanding of how it might work. Anyone have suggestions as to how to execute this project? Build it from scratch? Are there good theme templates I could work off of? Link to the theme I want to create: https://mywebspace.wisc.edu/staffanson/portfolio/files/sample_3/index.html

Cheers!