I have saved so much room, time and weight with flatstacks.
When I travel and take my food with me. I can pack a wider variety by packing into the portions and stacking in the Esky, when I reach the destination, I can just heat in the container, saves extra bowls/pots when washing wash up.
Going in the caravan with a smaller fridge they are just brilliant,
I use them to prepare, cook and serve in them saves on space weight and dishes to carry.
I love them, the no spill containers are the best such a plus when travelling....