Here's a picture of the finished product. I took the first screw out of the gas block and checked for fore-aft alignment upside down. Then I marked the block, and rotated 180. I tightened down the set screws to make imprints in the finish, and levelled the barrel in the vise off of the flat block bottom. Removed the block, hole punched in the imprints, and made the first set of dimples with a very small bit. After that, I stepped up to the final size.
All in, less than an hour. I took longer than many, since I set the depth stop on the drill press for each bit. Not taking any chances on going too deep!!!