After many iterations, I came to this final design that is very sturdy, stable and safe.
It is very easy to print, needs no supports, and will hold probably any lightsaber you have - I have had the chunkiest Rey saber hold up no problem now. (I dropped many sabers in the process to getting to this design)
It is exactly 6 cm wide at the flat side so that you can stick 2 strips of 3cm wide gorilla tape or similar double sided tape on it.
I recommend to leave a bit of tape “show” beyond the edge so that you can easily pull that to remove without any problems.
I do not advice to use this on wallpaper that could peel off, but it was no problem on a wooden wall or in my aluminum cabinet - of course :)
I printed this in PLA and of course PETG is even better - but both should be more than fine.
The author marked this model as their own original creation.