Are you interested in building a WP theme from scratch? If so, I found it very useful to see how the other themes work and what they are doing to display content in a visual appealing way. Then start building, as suggested above. Work your way down from the header to the footer, piece by piece. It’s always a good idea to search the web for something you’re interested in doing and learn how to do it.
I don’t know of a tutorial that will teach you how to build from scratch, but there are definitely tutorials out there about the little things. Put those together and you’ll build from scratch in no time!