Clean the oysters thoroughly and drain them in a strainer.
Soak the rice cake slices in cold water for 10 minutes.
Pour kelp or anchovy broth into a pot and bring to a boil.
When the broth boils, add the rice cake slices and oysters, and cook for 3 minutes.
Add minced garlic and green onion, then season with salt to taste.
Serve in a bowl and sprinkle with seaweed flakes.