There are carved cases and "molded" cases, and the molded ones you will find bent wood, or strips of wood glued to a "shape", almost like a basket, and then paper-mache over that, or just paper-mache outright in many cases, you just wrap the pipe and cut the thing off when it's dry.
The carved cases, like the Dunhill "ventage" cases... yeah they take serious time and it's not a casual undertaking. Took me about 8 hours to make one when I tried. I'll do it again at some point, but it's a "special" not a "daily" and for sure no one is paying me to carve a custom case for a 90 dollar Savinelli.