SLIDER BOXES AREN'T REAL BOXES
Created by: Exxion
They're children of /obj/item/weapon/storage/fancy/food_box
DESPITE LOOKING LIKE CARDBOARD BOXES AND NOT EVEN USING ANY OF THE FEATURES YOU GET FROM USING FANCY STORAGE
The main issue here is that you can't collapse them into cardboard Either resprite it to not plainly look like a cardboard box (and preferably use the icon updating features of fancy storage) or just make it an actual cardboard box.