To use:

1. Line the inside of the mold with plastic wrap (3d printed surfaces won't be food-safe)
2. Add some rice to the inside of the mold (60-75 grams of rice)
3. Press the rice with the knub side of the plunger
4. Fill the cavity in the rice with your filling
5. Add more rice(50-65 gram) and press with the flat side of the plunger
6. Remove from mold and plastic wrap
7. Wrap onigiri in nori (if desired)