If you want to run a marathon (26 miles), you can’t train by doing 1 mile every single day; you’ll need to build it up. Start with a 1 mile run, the next run is 1.2 miles, the next run is 1.5 miles, etc.
While doing one small site over and over will teach you some stuff, it doesn’t seem like the best idea to me — this way you’ll learn a lot about setting up a site, and building the scaffolding (because you keep doing it every day), but you’ll need to get into the more advanced stuff too. The things you do after working on a site for an hour.
Maybe start with smaller sites, but gradually create larger sites that will take you longer to do. If you just limit yourself to one hour for each individual site, you’ll never get into the more complex stuff. For example, how would you ever learn to do one of those headers that already take 4 hours or more?
Maybe have one site and do a new page every day within an hour?