I know several turners who have made them.
Probably the easiest way to go is find a picture of one you like and copy it.
The shaft is pretty easy.
Turning the disc requires a way to hold both sides.
One way I turn discs is to hold a square of wood against the top of the chuck jaws with thev tailstock.
Turn it round make a 1/8” tall tenon for dovetail jaws.
Put it in the chuck, drill the center hole, turn the face and sand it.
Then I put double sided tape on the finished face and press it against wood in the chuck with a face turned to a diameter a bit less than the disc
Turn the second face and sand it
Disc is done except for removing adhesive residue. Naphtha takes off the residue from my tape (got mine from woodcraft)
Alcohol removes residue from Some tapes