Separate the cabbage from the bunch and rinse. Spread a few leaves in a large shallow bowl and sprinkle with sea salt, about 1-2 table spoonful. Repeat the layer of the cabbage and salt. Let the cabbage soak for 1-2 hour until the they become wilted. Turn the cabbage upside down halfway through.
Rinse the cabbage 2 times and drain in a colander. Set aside.
Meanwhile mix seafood stock with rice flour and let it thicken over mid-high heat constantly whisking. Set aside to cool.
In a small blender, puree onion, garlic, ginger, shrimp sauce, and anchovy sauce until smooth. Add the fresh chilies and pulse a few times to cut into small pieces.
Pour the chili onion puree into a mixing bowl, add the Korean chili flakes, and the rice glue. Mix well. The seasoning paste will be slightly loose.
Spread the kimchi seasoning paste on to each cabbage so that it coats the entire cabbage evenly.
Store the kimchi in an airtight container for 1-2 days on the room temperature, then transfer to the fridge for further fermentation.
Notes
How to make seafood stock : combine 5-6 large dried anchovies, 1 piece dried sea kelp in 1-1/2 cup water. Bring to boil and simmer for 5 minutes. Discard the seafood and reserve the stock.