The ole clock on the wall.. or in the wall. Build in a simple clock that looks neat. Hand in mouth?

How to fit a simple clock in a wall. Yes it will be a mess to change the battery every now and then, but to me it is worth it. Don't put plastic in your mouth! I did it to hold the minute hand for a few seconds (No pun) and the foul taste was in my mouth for a long time (also not a pun).