This time it's a small box in sizes 10mm, 20mm and 30mm deep by abut 60mm max width. The lid is 10mm deep and hollow.
The boxes have special 0.2mm raft "wings" at the bits that often curl up. I was able to print in PLA without any curling at all. The raft breaks off very easily and very cleanly. Print with 20% infill.
Use "Customizable simple pin connector" (see "Derived from") to join the boxes together. The rainbow box in the photo uses the default settings for this thing. All the default diameters were designed for these boxes, so just change the length. TIP: make the slot good and long to get a flexible pin.
I have also provided a 17mm pin STL.
The rainbow box was printed using Rainbow Fun Pack from Faberdashery.