For a muzzleloader, decide about what you want based on traditional patterns then band-saw it out in 1/2" plywood.
Add shingle nails for sights. Pick a spot, close your eyes and bring the pattern up to check alignment.
Modify the pattern or make a new one until the nails align. May take three or four times.
Use this pattern to lay out your stock, but must look traditional. Easier with experienced riflemen, tougher with beginners.
Chuck