I love packaging bentos (japanese lunchbox), lunchboxes, dosirak's (korean lunchbox), etc. First off, I use the same 2 containers for lunch, so I know how to portion out by eyeballing them, taking out a lot of guesswork. Second, they are so easy to put together. If you have ever opened the fridge that belongs to a Korean family who cooks at home, you will find various containers full of banchan, which are side dishes. I'm sure you've seen these at any Korean restaurant. This bento would be vegetarian except I used ebi fume furikake, which contains shrimp. I don't fill up on rice, I try to fill up on vegetables first, which is what the sea tangle is for. My mom forages for this in the Pacific Northwest, but I'd advise going with a seasoned forager or expert, never assume wild seaweed is safe to eat unless you are sure of it. Also, be aware of seasons and changing waters, as they can contain many toxic waters.
I didn't have a banana for scale, but this box seems fairly small. It's actually the size of my hand, and the chopsticks are kid sized. I got them both from Daiso, and they fit perfectly in a bag I also I got from Daiso, a Japanese discount store.
I won't leave instructions on how to make each individual item, I just wanted to leave a description of what I used in the box. Sorry for the mixed measurements below, I just happen to know them off hand, but they don't match...
100 grams of steamed short grain rice
1 TBSP of furikake
100 grams of sea tangle
1 oz cucumber kimchi