Dissolve 1 cup of coarse sea salt in 4 cups of water in a bowl large enough to hold chopped cabbage.
Remove any bruised or very wilted outer leaves from napa cabbage. Split the cabbage lengthwise in half. Do this by turning the cabbage upside down, making a cut about 2 inches down through the core, then pulling the two halves apart. Split each half lengthwise again into quarters in the same manner. Cut off and discard the core out of the bottoms of the wedges. Cut each of the cabbage quarters into 1½ to 2-inch pieces.
Place the chopped cabbage in the bowl with the salt water. Add more water until the cabbage is submerged. Set aside for 1½ to 2 hours while you prepare the remaining ingredients, giving the cabbage a stir every 20 to 30 minutes.
Drain salt water from cabbage, rinse a few times with fresh water, drain, squeeze out as much water as you can with your hands, then set aside.
Make Kimchi Seasoning
Place 1 Asian pear, ¼ onion, ¼ cup garlic cloves, 1 tablespoon fresh ginger, ¼ cup fish sauce into a blender or food processor and blend on high until smooth. Add 1 cup gochugaru. Pulse a few times until well combined.
Make Kimchi
Add 1 cup julienned carrots, 1 cup sliced scallions, and 1 cup julienned Korean radish to the bowl with drained cabbage. Pour the Kimchi Seasoning over the vegetables and cabbage then stir everything to combiner hands (wear gloves!), spread the mixture over the cabbage leaves to makes sure they are evenly and well coated.
Pour the Kimchi Seasoning over the vegetables and cabbage then stir everything to combiner hands (wear gloves!), spread the mixture over the cabbage leaves to makes sure they are evenly and well coated.
Place the kimchi into large glass jars, pressing down to remove air pockets. Cover with lids.
Store the kimchi at room temperature overnight. After 24 hours, transfer the jars to the refrigerator. Kimchi will taste like a highly seasoned cabbage salad after the first day, and will start to taste like actual kimchi on the third day and beyond. Kimchi will keep for up to two weeks.