I removed the sanding surface and cut the foam sanding block in half
I glued the two halves together with 3m Super 77 Spray Adhesive.
I cut the foam into two 1 1/2″ x 1 1/2″ blocks.
I used a flat washer with screw and nut, also used some 3-M double sided tape to secure the foam block to the flat washer.
I used my drill press and 60 grit sandpaper to slowly form the foam block into a cone shape. You may want to wear breathing protection. The process does make some dust. It probably took me about five minutes to do.
The double sided tape becomes less sticky, so use new tape for each cone you do.