Seen something similar for forming spoons and small shallow dishes from horn. Very similar to a two-piece mold with a hinge, made from oak 2" thick. One half is the female shape, the other part is a male shape to nearly fill the female. Horn was cut, heated, flattened, then heated again for softness and pliability, placed in the mold and closed. Voila! A spoon & handle (or whatever) with just some edge trimming needed.
I found a high scrap rate with this process, as some horn does not flatten well and crack. Some items s formed in the "swage," despite going slow and heating for pliability, develop cracks.
I don't have enough experience to tell which horns in their round state will flatten and shape OK, and which will not. Perhaps there are some on this forum that can offer advice.