After printing a few of Wilhelnn's stackable trays to help keep my 3mm screws organized, I decided I wanted a way to keep everything together in a neat package - so I created this very basic tray rack.

The design has 1.5mm walls throughout, holds five trays and includes subtractions from the interior shelves to help reduce the amount of material needed. The front edges are notched to allow each tray to be pulled out easily. I have accounted for over-extrusion by leaving 0.25mm of space on all sides (0.5mm total on the width and the height).

Update - Added a version without the shelf subtraction. Use this version if the contents of your trays are prone to getting hooked while removing the tray, or if your hotend has a tendency to ooze during travel.

Printed on its back, no supports or rafts should be needed.