Cut the cabbage into quarters and remove the core. Cut each quarter into 2-inch pieces.
Place the cabbage in a large bowl and sprinkle with sea salt. Toss to combine and let sit for 1-2 hours, tossing occasionally.
Rinse the cabbage under cold water to remove excess salt. Drain well.
In a separate bowl, combine ginger, garlic, sugar, fish sauce, soy sauce, and red pepper flakes to make the paste.
Add the cabbage, green onions, carrot, and daikon radish to the paste. Mix well to coat all the vegetables.
Pack the mixture tightly into a clean jar, pressing down to remove air bubbles. Leave some space at the top for expansion.
Seal the jar and let it ferment at room temperature for 1-5 days, tasting daily until desired flavor is reached. Once fermented, store in the refrigerator.