In a large pot, fill 6 cups of water. Soak dried kelp in this water for at least an hour or overnight.
When ready, turn heat to low-medium and bring this pot (with kelp inside) to boil.
Keep boiling for about 10 minutes, remove the (now) enlarged kelp.
Lightly rinse dried anchovies (or dried shrimp, skip if use bonito flakes). Add this umami ingredient to water pot.
Chop off the root, and throw the white parts of scallion into pot as well.
Make sure heat is on low, simmering with cover for 40 minutes. Keep a small piece of folded paper towel between the lid and pot to avoid overflowing.
When done, strained through a sieve, discard the solid.
Let the liquid cool down, divide into portions and store in freezer for subsequent uses. This will be your Korean soup stock, can be used for Tteokbokki, noodle, etc..