Tbh, it might be a little bit hard for your first or second tries. But simply follow these steps (it will work like a charm!):
1. Make sure you have the right side. Place the small side of the lid over the small side of the box. (skipped if yours is one compartment)
2. Lightly press the lid down the box all around the corners.
3. Make sure there is no overlapping.
4. Lock all 4 sides, and ready to go!
The hako bowls are partly oven safe. Because they're made from 2 materials, plastic and silicone, thus they withstand different temperatures.
Plastic withstands 120°C
Silicone withstands 250°C
We strongly recommend you to take all the plastic components (lid and locking ring) out first before putting it in the oven. Otherwise, the plastic will melt;(