As Bridger mentioned, those plies are sliced. After all the plys are
glued up, the whole thing is put thru a huge sander, so getting the
veneer down to see-thru is no big trick.

Actually, when the panel is sanded, if it's sanded, it's not
sanded much. The ply starts life pretty thin. Back in "the
day" we used to get veneer as thick as 1/28". Today, OK the
last time I paid attention, it was down to 1/40". The thing
being, the more leaves you can slice from a log the more
cash at the end.

As for slicing, here's an animated demonstration.

http://www.wood-veneers.com/slicing.htm

UA100