Other IKEA KALLAX drawer inserts I found online where either too thick or too thin and they were all missing the configurations I wanted, so I designed my own. These boxes in particular have triangles on each corner to help them slide when they are stacked on top of each other. Every wall has a thickness of 1 mm.

Recommended configuration:

• top layer: 3 x IKEA KALLAX drawer insert - square slot 1 section
• bottom layer:
  • back: 2 x IKEA KALLAX drawer insert - square slot 2 sections
  • front:
    • IKEA KALLAX drawer insert - square slot 6 sections
    • IKEA KALLAX drawer insert - square slot 4 sections