A great book to find is Leather Braiding by Bruce Grant.
It's mostly about fancy braids with factory made flat lacing, but shows a lot of ways to make leather buttons and such and different lacing stitches to join parts of leather.
Which is applicable to sewing stuff together with sinew or other hand cut laces.
Another old favorite of mine from when I was a kid is Wildwood Wisdom by Ellsworth Yeager.
It's an old book that originally came out in 1945, but just has a lot of cool old fashioned stuff in it.
I used to do a lot of saddle and harness repair, seems like I had a book that showed a lot about the right way to do good double needle stitching, building things like sewing horses, etc. I have a ton of books stored away, I'll dig through them and see if I still have that book.
Unless a frontiersman had been around saddle or harness making it's doubtful they would have taken the time or had the stuff to do real complicated stitching.
They probably would have done their sewing with awls and whatever they had for lacing material.
At least for the stuff they were making with leather and rawhide.