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 (not included in the recipe). Repeat this process several times, changing the water each time.
Soak the rinsed rice in water (as specified in the recipe) 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 continue cooking 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.