Thanks for the good words!
I am not aware of any tutorial, it was a trial and error effort. The hardest part was finding the right chunk of the antler with just the right amount of surface curve to thickness ratio. Didn't want it perfectly flat and didn't want it too rounded so as to get the right amount of "bark". Once I got the slab to the right thickness I traced the profile shape from the factory wooden insert onto the antler slab. I then used a belt sander clamped upside down in a vice to carefully sand the slab down to the line. Lots of sand, then fit, then sand, then fit and so on until I got it just right. To get the screw hole in the right place, I put one side into the rubber grip, marked the hole through the grip, and then removed, clamped, drilled in my drill press. Once I had a hole in the one side, I clamped both sides together and went through both on the press.
That's the quick and dirty. Hopefully it makes sense. If you have any more questions let me know!