Trent Watts has made a couple of forms for making felted hats.
A friend of mine makes wonderful felted hats and needed a mould close to the size of her head. I found a couple of bowl blanks I received from Larry Matisho many years ago. I needed both pieces to create a deep enough form to mould the wet felt into the shape of a hat. There was some initial turning to get the pieces round and then I used sanding disks to reshape the form into an oblong human head shape. The wood is finished with Watco Oil and then sprayed with lacquer to help avoid problems from the wet felt.