There are jigs available to guide you on the drilling. There is a fair amount of work to be done to complete the lower, but it can all be done on a drill press. CNC would be better for these, but not necessary. Without the jig, I wouldn't even try to complete one. Here is a site that carries the jigs. Jigs

"What's the point of being retired if you can't climb trees and wash your feet in the creek?" - Teal