A remix of jefftml's design where I've combined the parts together to avoid the need for glue. It still uses the “small” size command strips for mounting, but I've also created a variation that uses two M4 x 16 screws.

Both versions should be printed laying on the back of the mounting hardware, i.e. the slots for the watch straps should be vertical. In my testing, since the angle of the slots isn't too extreme, it should print fine in this orientation.