Step 1
Remove discolored bruised outer leaves of cabbage and rinse cabbage under cold water. Cut cabbage head into 2-inch pieces.
Step 2
Divide 3 cups water among 3 bowls. Stir 1 cup sea salt into each bowl of water. Sprinkle the remaining 1 cup sea salt over cabbage.
Step 3
Place salted cabbage in the 3 bowls salted water until partially submerged; let sit 6 to 12 hours.
Step 4
Rinse cabbage thoroughly under cold water several times. Squeeze cabbage to remove excess water. Cabbage should have a rubbery texture. Transfer cabbage to a colander or basket to thoroughly drain the cabbage at least 2 hours.
Step 5
Combine 3 cups water and rice flour in a saucepan; bring to a boil. Whisk mixture until a glue-like consistency 5 to 10 minutes. Remove saucepan from heat and cool rice mixture to room temperature.
Step 6
Combine onion garlic ginger and 1 tablespoon water in a food processor; pulse until smooth adding more water if needed.
Step 7
Pour chile flakes into a large bowl; stir in onion-garlic mixture cooled rice flour mixture fish sauce shrimp brown sugar and sesame seeds until well mixed. Add radish and green onions and mix well.
Step 8
Coat each cabbage piece with chile mixture by using your hands. (Rubber gloves are highly recommended.) Pack coated cabbage leaves inside air-tight glass jars or containers; cover each tightly with a lid. Keep jars at room temperature for fermentation to occur about 2 days. Refrigerate kimchi after the 2 days.