I've used some of the methods mentioned above with good success. Instead of using a router bit I use a drum sander with a bearing on it. The drum sander is chucked into a router set into a router table. Use only a variable speed router at LOW SPEED. You can also chuck the drum sander into a drill press, but the template would need to be on the bottom using that setup. I cut the ribs out to a rough size on the bandsaw first. Sanding drums are available at woodworking supply stores like Woodcraft.