The building instruction book that comes with Vaclav's plans also contain good instructions on how to cut and mill your strips. The instructions that come with Rob Mack's designs (LaughingLoon) also contain good instructions on how to mill your own strips. Many posters here have used Nich Schade's book, although I haven't read it. I followed Vaclav's plans from the start, including the directions on cutting/milling the strips. You don't have to get completely knot-free boards, but they need to be clear enough to cut strips. I used 16' western red cedar from a yard here in the Cleveland area.