I’m impressed with those cardboard boxes, too! Expandable! Where do you get those big ones? Are they new moving boxes, or something you found?
Those are actually Weber grill boxes from our local hardware store. Each spring I contact the warehouse manager and assembly guys since they sell and assemble a lot of products. I ask them to save 2-4 identical boxes instead of putting them in compactors, I pick them up collapsed to fit in my car, in turn I bring them some fresh eggs since I told them I’ll be using them for chick brooder. When I’m done with boxes, I bagged and compost the shavings or directly place them on our hedges and I return the used boxes back to them to recycle.