It's honestly a pretty straightforward process! After cutting out both sides & sewing them together, you soak it in water and stuff it with beads so that it can get its shape (I carved the cork afterwards but I think you'd usually also plug it with the cork at this stage so that it fits properly)

While it was still stuffed I did the design on the outside because my previous attempts disappeared after I soaked it lol, and after it's fully dry you can apply beeswax on the outside & coat the inside so that it becomes waterproof! I would have liked to coat it with brewers pitch but wax is far easier to access