Obviously, I've gotta go first:

THE TASK AT HAND: Taking a half-cut tree round and efficiently cutting a round bowl blank, which isn't easy with the irregular bark or burl shape.

THE NIFTY TIP: Take a round piece of masonite or plywood, place it on top of the irregular surface, then sprinkle line string chalk (flour will do) marking the round blank where it falls vertically. If there's any danger of the chalk falling off during the ensuing bandsaw cutting, spray it with whatever finish (or hairspray) to lock it in place.