I've done this on both of my kayaks. I made a template out of plexiglass for my plunge router to cut the holes in the kayak. By using double face tape to attach the template to the kayak, a straight cut bit, and a colar on the router, the slots come out perfect. I used a file to square up the slot. I also made a simple jig to cut the same size slots on the stips of wood that make up the straps. I would also make twice as many as you think you need so you can choose the best ones or easily add more later. (The webbing sucks up the epoxy and makes a some a bit stiff near the bottom.) Use black RTV silcone to put them in place and they can be removed when you want to re-varnish the deck. Good luck....Greg