I trace a template with a fine line marker, then cut them free hand with a #11 blade. Ribs aren't structural, so choose a weight and thickness that is easy to cut. I'll stack sand them after they've been cut out. The spar slots turn out good while the ribs are stacked in a bundle. By the time some geek loads his coordinates and sends them off to a cutter, then waits for delivery....I'm already wiping oil off a finished plane.