some of the previous forum topics
Recovered saddles...
Use for frames from defunct leather saddles?
Saving a dead Brooks.
where I also make reference to my recover.
I also caution against heating the leather above 70C as it can cook it, and make it brittle (references given)

I made a plaster mold, 6-7mm thick vegetable tanned butt leather (try you shoe repair shops for their source for shoe soles), vacuum bag, countersunk machine bolts and this was the result.

afer 1000km it is making a nice shape.

My second recover, just finished, was a little more interesting; I modified the cantle plate, arching it and flattening the rear together with narrowing the width. seeking to be sympathetic with this and this
here is the work in progress

After I finished the trimming, and swapping over the bolts, it was given two dressings of Proofide and it had its first outing last Sun. Very comfortable.