I re- saw solid lumber into thinner layers and the glue it back together with a 1/2" base layer of walnut then 1/8" of cherry and then 1/8" of maple. The sphere will be all white maple until it is sanded round which exposes the different colored woods below. The concept is the same as the Baltic plywood sphere, but I just make my own "plies" of wood.
 
The pentagon shaped hole is rimmed with 1/8" aluminum.