I'll watch for that link, too...
Got a couple so-so seats I don't want to give up....
I guess they use a paper pattern, for starters, when cutting thinner leather for a cover, then stitch it.
A thick leather seat could be made from a raw hide, wet, then clamped in a mold to form it.
But I've never done one before...
I do know it's real difficult to stitch leather without a real machine, and stitching in a straight line is also a difficult thing to do! lol
Best
rc