Rehydrate dried wakame in water, then cut it into ⅕-⅖ inch (5-10 mm) cubes.
Place a sieve over a bowl, add rice, and rinse it with water. Repeat this process several times, changing the water each time.
Soak the rinsed rice in water (as specified in the ingredient list) in a pot for at least 30 minutes.
Add seasonings (sake, mirin, and salt) to the pot and mix.
Cover the pot and bring it to a boil. Once boiling, reduce the heat to low and cook for 10 minutes, or slightly longer for larger quantities (11 minutes for 4 servings, 12 minutes for 6 servings).
Turn off the heat and let it steam for 10 minutes with the lid still on.
Remove the lid, then add the wakame pieces to the rice and mix.