So this is only the second insert I've made and the first I've felt brave enough to publish.
You only need to print one of every piece, and they should all fit together fairly intuitively. I've attached enough reference images to help, hopefully. Also attached is an image of these boxes painted to fit their faction colours by woodland warriors discord user meadowdrone.
Bilby3D 1.75mm PLA+ PLA
All the walls in this design are in widths that are multiples of 1.2mm, so this design will work with 0.2, 0.4 or 0.6mm nozzles. I've designed the sliding trays with a tolerance of 0.5mm which slides well on my printer, but I have ever so slight bulging on the corners of my prints which may influence that a bit.