Using a 3/16" drill bit I apply a "high tech" depth guage at about 1/8" and
drill randomly spaced holes around the sphere.
Now it is a matter of hollowing the sphere until
the holes are exposed leaving a uniform thickness of wood.
Once the sphere is hollowed, use a straight tool to make a series of cuts through the bottom and
into the glue block leaving a mortise for a later tenon. Part it off along the glue line.