It’s important to pack the foods tightly to prevent the food from shifting in bento box. You don’t want to see messy bento when you (or your children) open the bento box at lunch time. Try packing in following order.
Pack pre-shaped or bulky food first.
Then put more flexible-shape food in remaining spaces.
Finally add some small accent food like cherry tomatoes and steamed broccoli to fill in the small gaps to prevent from shifting.