I chose to 3D print the enclosure with built-in stand-offs for the Arduino Mega and RTC module. Autodesk Fusion 360 was used for Modelling. 3D printer was Craftbot Plus.

The small groove in the bottom exists to allow a screwdriver to pop out the faceplate if required.

The intention is to wrap the box in wrapping paper, so a top faceplate was designed as a snug fit to cover everything up.