Remove the battery from the LCD clock and make a notation of which sides held the positive and negative contacts.
Mark the potatoes as No. 1 and No. 2 with a marker.
Insert a steel nail in the one side of each potato. Allow 1/4 of an inch of the nail to stick out of each potato.
Insert a 1-inch copper wire in each potato on the side opposite the nail. Allow 1/2 inch of the wire to stick out of the potato.
Attach one end of an alligator clip to the wire in potato N. 1 and the other end to the positive contact in the LCD clock.
Attach one end of another alligator clip to the nail in potato No. 2 and the other end to the negative contact in the LCD clock.
Attach one end of a third alligator clip to the nail in potato No. 1 and the other end to the copper wire in potato No. 2 and turn the clock on