When you have the need to set an engagement ring and so very worried how to do it. This is the way I've been taught. In the first photograph you will see a bud bur carve a little groove 1/3 from the top of the claw/prong, why do this? The reason is so-o simple, it will prevent the HSS, 45-degree angle bur from cutting too high up the claw/prong. You need that 1/3 remaining for filing & 'trimming' of the claws!
Then after this is done, use your great HSS bur and create a seat for the upper-section of the Pavilion, not the whole inside to the top to the bottom, of the claw.
Before you close up the claws, there is something you must realize is that on every claws you will find a little extruding piece of metal where this bur created...clean it up with a #180 grit, pumice wheel! Once the diamond is in, it's literally impossible to reach. I am a great proponent of using this #180 pumice wheel.It is very gentle, but still strong enough to remove any plier or file marks. In front of the Flat Top claw, I use a triangular file of #4.grit and file on the side of the file and it will give you a front edge of that claw/prong. I even use my Tapered, Pumice Wheel to clean everywhere. Once the ring has been completed, you may polish it so gently, as to not round off any sharp edges that you created !!