A main reason many people like to, or want to, make bento lunches is for more variety, to save money, and to have some fun too. In my mind these aspects are quite interconnected.
There are three sources for filling your bento box. One is food that you make specifically for it, usually in the morning or perhaps the night before. The second is leftovers from other meals. The third is with stock or staple items (aka johbisai). The key to keeping a good variety in your bento meals is to use all three sources in in a smart way.
Certain foods are just better when they are made fresh. Raw vegetables for example, which need to be crisp. Some protein based foods go bad fairly quickly unless they’ve been cooked in a way that preserves them, so it’s safer to eat them as soon after you’ve made them as possible. A good example of this is tamagoyaki (Japanese omelette) .
Unless you have a lot of time to spare though, you’ll probably want to limit the number of things you just have to make fresh in any given bento box. Once you get more experience with bento making, your speed and efficiency will increase. But if you’re just starting out, try to plan bentos that may have at most 2 to 3 items in it that have to be made in the morning.
Using up leftovers for bento is a great way to both increase the variety of what goes in there and to save money. You save a lot of money by bringing a bento vs. buying something or eating out anyway, but you can really maximize your savings by using leftovers. The first and easiest step is to just set aside some of your dinner and to put in your bento box the next day (or freeze for later use).
To go a step further, try to think of varying the flavor or texture of the leftovers. I love to think of how to make something ‘different’ to have in my bento whenever I’m making dinner. Here are some ideas to get you thinking about your own repurposing variations:
Safety note: Always re-heat leftovers before putting them in your bento, or else freeze them and defrost - especially things with protein in it!
See also: Top 7 things to do with leftover food scraps  on Lunch In A Box.
The final part of the bento variety puzzle is a good stock of staples. Every Japanese bento maker relies on a stock of johbisai (joubisai) or staple items. These can be homemade or bought. These are items that can be kept for a period of time and pulled out and used on short notice. They can be stocked in the fridge, in the pantry, or in the freezer.
There’s a growing list of johbisai recipes here on Just Bento . You don’t have to make everything you stock though. Here’s a list of some readymade foods that are great to have on hand. (I’ve classified Japanese staples as ones that you would need to go to a Japanese grocery store for. Things like edamame are now getting stocked at non-Japanese markets like Trader Joe’s too, which is great)
One important thing to remember though - don’t get carried away with stocking up on staples, especially if you’re trying to save money! Even long-keeping foods do go bad eventually.
Next week I’ll be back posting actual bento step-by-steps and recipes. Enough theory, more action!