Twelve South makes some great Apple accessories. The Time Porter watch band holder is no exception, however upon looking at the design I thought that cannot be that hard to make. It looks like there are no magnets or other elements to hold the bands in place other than a little tension and good engineering of angles. Based on photos from their webpage, I re-created this to the best of my design skills.
The smaller of the two was my test print. It can hold exactly 1 Apple Watch as shown in the photos. Once I proved that worked I scaled up the middle part to 145mm.
Print the middle section as one body and stand it on end with a brim for stability. It will come off the bed as two parts, a top and a bottom. These fit snuggly into the end caps that I created. Though I labeled them Left and Right they are essentially the same cap.
The author marked this model as their own original creation.