The enclosure for my printer is similar to the Prusa Enclosure V2, with a lid that the spool boxes sit on. These table mounts keep the boxes in place and neatly aligned. They also allow opening the lid without the boxes falling off.

The mount is fixated with two 3.5mm screws. There is a felt sticker on the mount (see fourth photo), to create enough friction with the box without scratching it.

I designed the model with CadQuery. The Python script is among the model files.