Material was selected for the legs and roughly cut at the band saw. At this stage I am looking to create reference surfaces for the legs while leaving as much material as possible for future shaping.
One of the front leg sticks had punky area at the bottom which I hoped would be outside of the finished area. However, my confidence diminished as I pondered the process, so I chose another stick to work with. It had its own issues, but I will not know the outcome until further along the process.
I jointed the rear legs enough to have reference faces, then used a hand plane to create a flat and perpendicular area for the joinery. Dadoes were cut on the table saw to fit notches at the rear of S3. When a tight fit was achieved, a round over was cut at the router table. The round over and dadoes match the notches and rabbets on S3.
Front legs were similarly created other than this joint is less secure, being only captured on two sides (rather than three on the rear legs). Cutting those dadoes and round overs only required one good corner. After test fitting, the entire stool was dry assembled for a photo op. Not so elegant at this stage, but the foundation has been laid.