Modified/combined in SketchUp. It has nail/screw holes to mount easily to the wall. I recommend printing the mounting sleeves in TPU to avoid scratching your ukulele.
Also, Octagram Spiral looks great as the top infill pattern.
The triple was printed on a Prusa XL and filled most of the bed.
The author remixed this model.
I combined the turtle design and wall hanger into SketchUp to make a single, double, and triple ukulele holder.