Boil the buckwheat noodles in boiling water, then rinse with cold water.
Grind perilla seeds and put them in a pot with water, then bring to a boil.
Once the broth is boiling, season with soy sauce and salt.
Place the cooked buckwheat noodles in a bowl and pour the perilla broth over them.
Add seaweed flakes and green onions to taste.