another proposition... an intersection of spheres

4 spheres made with circular array.

You boolean intersect them.
Next you cut to have only the mid top.

Next you chamfer the bottom.

I have made a second version with opposite spheres scaled with 0.1 mm less if you want the edged top.

Adapt the height as you want...


To have surfaces for the claws, rotate your stone and cut with a curve.

All steps inside the 3dm file