Customizable Square Tray with ZipTie Mount

My girlfriend's father has a workshop, with some pillars holding the ceiling up. I thought "I should print some square trays he can mount, to hold drill bits, etc."

This is a remix of the customizable square trays, with holes for zip ties. I've also angled the top, which I think is better for when the tray is tethered and can't be picked up.

Please leave suggestions for improvements in the comments!