I set out to design a shelf that could attach to my refrigerator and give me more storage space for small items. This shelf/box can support a large quantity of light weight objects such as chip clips or other various items that everyone always needs but can never find in the kitchen. The dimensions are 218mm x 103mm x 75mm, 4mm thick and requires 18 - 8x3 magnets. The prototype was made using 6x3 magnets so the version I uploaded should be able to support additional weight compared to my tests.

I would recommend printing in 0.2mm layer height, 2 walls minimum, and 15% Gyroid infill. The magnets should be nice and tight and not require glue to install, however you may need to push really hard. Tolerances of course may vary depending on your printer's accuracy. It is not recommended to resize the model because it will resize the magnet holes.