That one and a few others like it, were slotted by using an 8" composite metal cut off saw blade, mounted in a bench grinder. The problem was that since I have not figured out a holding jig for the antler, they were free handed, and I would screw up as many as I got right. The cut off blades can burn you and draw blood if you slip up, but are relatively safe when compared to a table or other type of power saw. The metal cut off blades do a good job if one can just keep things straight. If you can get the slot well started and true, you can finish with a Dremel tool to get the final depth.