The "ivory" is the ear bone, otolith is the proper term for them. They sit a little aft of the brain, and the brain stem comes up between them. Using a butcher knife with some heft to it you chop down and back at a little less than 45 degrees. If the blade is heavy enough you can likely cut deep enough with a single whack.
A tweezer will help you find one down in the liquid in the cavities on each side uncovered by the cut. If there are no cavities showing you need to cut a little deeper until they do show.
