This is a big part of my eventual FI plans- a tiny house in rural Western Virginia. I've thought about it a lot!
I'm actually planning on designing my own, but I will hire a professional architect to mock up the official plans. My tentative plan is to hire a contractor to do all the hard stuff like framing and putting in windows, plumbing, electric, etc., but I want to do all the finishing myself (things like painting, staining the wood, and anything else I think I can handle).
This is still a good decade+ for me, so I'm hoping that in the interim, I will be able to make friends with some craftsmen and women who are able/willing to assist me. My parents built their own house with the help from a lot of talented friends, and I really like the pride they have in knowing they had a hand in building the home that they live in. What an accomplishment!