Based off the decorative pillbox available here

Pocket watch casing for an old pebble time (square) with integrated mount for the pebble and open back so you can charge it without needing to remove the watch from the casing.

The mount itself is designed to be used with the strap pins in place, which means that its also easier to take out and put back on a band if you so want.

Prints in 2 sections ;

Upper Half / Lid - I recommend you print this as orientated with supports.
I got a good result using a support thickness of 40% less which made them easy to remove and left the patterned surface on top which results in the fine detail looking nice.

Lower Half - Print any way you want - It shouldn't need supports, but you might need it depending on your printer.
I used supports for the hinges - but I'm not sure it's necessary.

Tolerances are a bit generous which means it should come out reasonably well on most FDM printers.

Hinge pin - I designed this to use a length of 1.75mm Filament as a hinge.

A spot of glue at each end of the hinges should keep it in place while allowing the hinge to work.

I've also included the mount I designed for the watch itself separate print file, in case you would like to drop that into anything else/use in a remix.

Designed in TinkerCad.

Pattern - Hand drawn in Sketchbook Pro for the iPad.

Initial versions printed on FlashForge Adventurer 5M / .4 nozzle / Layer Height .10mm