Prepare the cabbage: Cut the napa cabbage into quarters and remove the core. Slice the cabbage into bite-sized pieces, then place them in a large bowl. Sprinkle the cabbage with sea salt, ensuring the leaves are evenly coated. Add the water to the bowl to cover the cabbage. Let it sit for 1-2 hours, tossing the cabbage every 30 minutes to make sure it evenly wilts and softens.
- Prepare the kimchi paste: While the cabbage is resting, make the kimchi paste. In a small saucepan, combine the water and rice flour, bringing it to a boil over medium heat. Stir frequently until it thickens into a paste, about 2-3 minutes. Remove from heat and let it cool. Once cooled, add the grated ginger, minced garlic, fish sauce (or soy sauce for a vegetarian version), Korean red pepper flakes (gochugaru), and sugar to the paste. Stir everything together until well combined. This is the flavorful kimchi paste that will coat your vegetables.
- Rinse and drain the cabbage: After the cabbage has softened and wilted, rinse it thoroughly under cold water to remove the excess salt. Drain the cabbage well, ensuring there’s no excess water left, which could dilute the kimchi paste.
- Combine the cabbage and kimchi paste: Once the cabbage is drained, transfer it to a large mixing bowl. Add the radish slices, and then toss in the kimchi paste, using your hands or gloves to massage the paste into the vegetables. Make sure every piece is well-coated in the flavorful paste.
- Pack the kimchi into jars: Pack the kimchi into clean, airtight glass jars or containers, pressing the mixture down to ensure there are no air pockets. Leave about an inch of space at the top to allow room for the kimchi to expand as it ferments.
- Ferment the kimchi: Leave the jars at room temperature for 1-2 days to ferment. The length of fermentation will depend on the ambient temperature—warmer environments will ferment the kimchi faster. You can taste it daily to check its tanginess. Once it has reached your desired level of fermentation, transfer the kimchi to the refrigerator. The cooler temperature will slow down the fermentation process, and the kimchi will continue to develop flavor over time.
- Serve: Kimchi is best served cold, straight from the fridge, but can also be used in soups, stir-fries, and other dishes. Serve it as a side with rice, on top of noodles, or as a topping for tacos, fried rice, or sandwiches.