Hi Lin,
I usually use the nose portion on my chainsaw to carve out the bowl in the stump.Please have someone who uses a chainsaw often to do this task for you, it is VERY DANGEROUS!Kick back from the saw is likely, try to use the bottom half of the nose.
With these stumps I free-handed the cut using a regular power circular saw. I plunge cut a series of cuts then did the same from a different direction.Kind of looks like fork impressions on a peanut butter cookie. You can clean up things by dragging the saw blade sideways, or use a wood chisel gouge. I smoothed it all using a course sanding disc on my angle grinder. A bump or two can be smoothed by hammering them down.Good luck and please be extra careful.
Peace,eh
Frank

Hi Lin, they actually make a wood carving blade that goes on your 4-1/2" grinder, a tool you might have a lot more experience and confidence in using since your a metal worker. It sure would be a lot easer to use and hang on to.

Here is a couple of them:

--King Arthur Tools Lancelot Woodcarving Disc, 22 Teeth, 7/8 Arbor

--Arbortech Pro 4

Hope this helps

Jake

Jake Balcom
Mettle Design
Lincoln, NE