Cool! I cut up Ritz cracker boxes and mac-and-cheese boxes to make small holders ("trays") for various things.
Four cut-down pill bottles fit into a Ritz tray, and they hold four 2x3" Ziploks propped up with small funnels, so I can spoon seeds into them. (photo needed!)
When I run out of plastic trays, I use larger corrugated cardboard boxes lined with heavy garbage bags as trays for plants in 4" pots and Solo cups and yogurt quarts. They can take more weight than flimsy 1020 trays!
But you can't put them outside on damp ground or the4 cardboard turns to mush.
The cardboard trays are front-right and front-center. (Better photo needed. That's a mirror in the background.)