After finding that varying sizes of trays can be useful for organizing and storing anything from small parts to full size documents, I looked for something already existing. The problem is that I also wanted some flexibility in the size so that these could also be used to organize drawers for example. After failing to find a sufficiently flexible design, I decided to give it a try myself.

In this case, the design is done in Fusion 360, and many of the parameters are adjustable, depending on your needs. In particular, the length, width, height, wall thickness and wall angle can be adjusted within F360. One could add additional adjustable parameters, I suppose, but you get the idea.

Many of these examples have a wall thickness of 0.03", which is about 0.75mm. At this size, the trays are fairly flexible yet sufficiently robust for my purposes. Obviously, for large trays, the printing time becomes significant.

Wall angles up to about 10 degrees seem to work fine. Note however, that there are some extreme conditions wherein the model will fail--especially large wall thicknesses on small-ish boxes and steep wall angles.

I have uploaded the F360 file and a few of the Sketchup files.