Don't do it from scratch.....it's a LOT of work for no reason, and in a few week's time, you'll realise that there is a folder structure missing and have to start all over again.
Use a very simple, basic design them modify the CSS to make it an entirely new template.....that way, you'll at least know the underlying structure is there and complete
There are thousands if not tens of thousands of templates to base a design on......using the in built search engine from within a WP install, you can look for the very basic needs then test each one out and look at the CSS to make sure you can use it