When you finish eating, fold it to make it compact. I found a goods called "Lennon Folding Lunch Box with Partition" that is convenient for carrying sandwiches. I actually used it.
A lunch box for sandwiches sold by Pearl Metal. It is an assembly type and can be folded to make it compact after eating the contents. The thickness (height) when folded is about 15 mm, which makes it easy to store in the kitchen. People who already have some bento boxes can easily buy more.
The size when used is about 175 x 105 x 75 mm. It was a good size to put two butter rolls and a little side dish. It seems that it is also suitable for putting rice balls, and it seems that you can take photogenic pictures if you turn the cross section that looks delicious.
Since it is not a closed type, it is recommended to wrap the food in wrap or foil before putting it in. Also, if pressure is applied, the lid or basket insertion part may come off. It may be better to avoid using it on days when you plan to take a crowded train.
It is available on various mail-order sites, and I purchased it for 695 yen using Amazon.co.jp. In addition to the blue color introduced this time, there are brown and red colors. There are various types of foldable lunch boxes available from each company, so why not try to find one that suits your eating habits?