Read all the tutorials at the top of the Reelfoot forum. I get the rise angle by inserting a spacer block under the end of my tone board jig and then cutting the tone channel to depth with a round nose milling cutter. You can make the cut with either a mill or a drill press and an X,Y table.
Antique calls were made by drilling the tone channel hole at a 5-6 degree angle and then cutting away the waste . The resulting tone channel will be at the angle of the drilled hole. The further down you cut the shorter the resulting tone channel will be.
Fred