Finding "the pith" in olive is easier said than done. Those old trees
are usually so gnarly you'll mostly be fighting voids that are all but
invisible on the surface.

If it's like the olive I've dissected, you'll find the hardest thing is
figuring out how to get a bowl out of it without having holes through
it. don't worry about "the pith" except to remember it's going to have
the best chance of having good solid wood without holes and bark and
dirt hidden in it. If you cut it in pieces to "cut out the pith" and
only later realize you've cut out the only solid wood, that's a shame.

MOST IMPORTANT THING: clean out all the dirt and rocks with water and
crow bars or re-bar or something before you go cutting anything with
dirt and rocks.