Here's something a nubee told me I wish I'd thought of 40 years ago, thought I'd pass it on.
When I paint boxes, the tops & bottoms & joints get painted by doing them in the stack before the boxes get assembled. Then the boxes are assembled, get 2 coats paint & left to dry for a day before getting stacked alternately as per the pic.
Here, the problem. The paint where the boxes are touching each other is dry, but only a day or two old so still soft. By the time I come to use the boxes they can be firmly joined together and you have to sometimes break wood getting them apart.
So, here's the tip. - While stacking them, have a rag soaked in cooking oil and give the contact points between supers a wipe with it. Doesn't seem to hurt the paint and the boxes come apart much easier later.
Who said old dogs cannot learn new tricks.