My brother traps and got a beaver. He tanned it himself and wants a pair of chopper mitts. Since the hide was not professionally tanned its not been thinned and its not as soft or pliable as I would like but the fur is great.
In the picture below, the head is to the left. The thickest part of the hide is near the neck and down the spine. Its thinner at the belly so each mitten will have varying thickness unless the leather is thinned.
The thickest portion is nearly a 1/4 inch. Your seeing the finger tip area (thickest) and the thin part is from the other mitt in the wrist area. These thicknesses need to be the same or the mittens will be too stiff.
Thinning and oiling makes the hide a bit more flexible but the hide is not as flexible as a professional tanner would make them.
Then the two halves are sewn together inside out.
With the aid of time and a broom handle they are turned right side out. Its delicate work not to damage the hair.
I made the liners for the mittens using polar-tech fleece. Its thick and warm and soft.
Here my hand model wears them.
The liners are inserted into the mittens and my hand model shows how the finished mittens look. They are heavy and thick and warm. They should last a long time.