What's a good way to customize or recess a lightswitch?
I would not recommend this. Switches are tested to electrical safety standards which includes making sure they have adequate insulated properties that prevent you the user from getting a shock. They are also designed to drain a short circuit to the earth/ground by cross bonding metal components built inside the switch. Modifying a switch could invariably invalidate those safety features. Making it a hazard for you and anyone else using said switch.