Inspired by the single watch stand by TIM, I have modelled a modular system that grows with the number of watches you have. The modular system comprises three base types:- a Left end base, a Middle base and a Right end base, each with a snug dovetail fit to the adjacent base.

Along with the expanding base I have modelled two stand types. One fits larger mens regular watches and the other is an adaptation to accept an Apple watch charging base with provision for cable lead out.

The fits are designed to be snug. I have also modelled into the base elements and the stands recesses for 5mm Neodymium magnets. 

UPDATE - 3mf file updated to include the smaller watch stand as well.