Update 11.15.2023: I added a new version which is “open” on top, to ease the insertion and removal of the charger. Looking at some of your comments, the “closed” version can be too tight depending on the material, printer...
When I printed the model from Aiirik, the charger didn't stayed inside the hole, popping on top because of the constraint on the wire. Therefore I decided to redesign this stand from scratch to prevent this issue, and also to improve the edge in front to better match and maintain the Apple Watch (I feel it more secure :-)).
I used the model from Peterson to better position the watch and follow its shape for the edge.
Fusion 360 and STEP files are included to allow remix culture :-), or if someone wants to remix or adjust the depth of the hole to fit with old metal chargers which are a bit thicker than the one coming with this watch.
Works with a MK3S+ as is (just a blow of cutter on top of the hole because of quality of the overhanging).
If you face problems inserting the charger (especially with aftermarket ones, or based on your printer capability), you can slightly upscale the model to increase the size of the hole.
The author remixed this model.
Enhance the stand design to perfectly match the Apple Watch Ultra shape.
Additionally, include an "open" variant to facilitate the insertion and removal of the charger.