If you didn't have a 3D printer, you could still print a template on paper, glue that to a board, saw/rasp/file/sand to the line and then use the shaped board as a template. Double sided tape should probably be good enough to keep it in place on your actual workpiece.
If you didn't have a 3D printer, you could still print a template on paper, glue that to a board, saw/rasp/file/sand to the line and then use the shaped board as a template. Double sided tape should probably be good enough to keep it in place on your actual workpiece.