Or just don’t “construct” them to begin with. I always get a kick out of how just about every student will take their sandwich or burger apart before eating it. Even salad ingredients get separated out before children eat them. Some items will still be combined before they’re eating, but usually speaking, food items don’t stay as they started. Instead, put all the components into the lunchbox and let kids have fun putting them together as they’d like. It’ll save everyone time!
One of the most successful lunch options for keeping things deconstructed are home-made Lunchables or something else that’s easy to stack. Again, let your child choose the items. These are by far some of the best eaten lunches I see in the cafeteria.