I saw someone on here cut some lam's and glass about 2" longer than the riser.( a stack about 1/2" thick)
Put half of your bow stack on the form. cover with plastic wrap. then
glue up the riser stack(template) in the form with the air hose, after curing, use that on a piece of plywood as a template to sand the riser template.
I did it the other day and it work like a champ.
Double side tape my stack and a 2x4 to a 3/4" piece of plywood. run that threw the thickness sander.
flip that over and use your pattern sander to make the template.
mine was 1-1/2" wide