Tom
Hey Art, you’re in my neck of the woods.
Respectfully, I would not advise a grout or plaster of paris leveler.
The bowl has a less than 1/2″ lip around the perimeter of the base where it contacts the floor. Any masonry product will , in my experience, not hold up under those thin (1/16 to 1/8 high and 1/2 wide) conditions.
The stool may be stable today, but won’t stay that way as the thin base crack out.
