there is a bolt with a slotted head in the Ithaca butt stock. When ever I need to take mine off, I take a driver bit and tape it into a 1/4 driver socket. Then I wrap masking tape around the socket until it is built up just enough so slip into that access hole. The tape will keep the bit in the slot.
There is also the possibility you might have a socket that will fit the stock bolt also. Regardless, trying to do it with a screw driver is a definite PITA.