Quarter the cabbage and discard the root. Chop the cabbage into bite-sized pieces. (Roughly 1.5in x 1.5in)
Add to a large bowl, sprinkle the full amount of salt over the cabbage. Toss the cabbage to coat evenly as you sprinkle. Set aside. Toss again every 30 minutes for a total of 1.5 hours.
Add the rice flour and water to a medium pot. Bring to a boil over medium heat, stirring occasionally to prevent the rice flour from sinking and burning. When the mixture begins to boil, add the sugar and continue stirring while it boils gently for 8-10 minutes. Once the mixture turns shiny and thickens, remove from heat and set aside to cool completely.
Julienne the radish and carrot. Chop the green onions about 1in long. Add to a medium bowl and set aside.
Peel the garlic cloves and ginger and add to a blender jar. Toss in the onion and fish sauce. Blend well. Set aside.
After the cabbage has salted for 1.5 hours, rinse (3x) and drain thoroughly.
Add the cooled porridge, the fish sauce mixture, and the gochugaru to a large bowl and mix well. Add in the julienned vegetables and green onions; mix well. Drain the cabbage one last time and add to the bowl, tossing with gloved hands to combine.
Distribute the kimchi evenly between five wide mouthed mason jars. Use a fork to push the vegetables down below the liquid and remove air pockets. Seal and allow to sit at room temperature.
After 24 hours, open the jars and use a fork to push the vegetables down again removing air bubbles. Seal and continue to rest at room temperature.
After another 24 hours, open the jars and use a fork to push the vegetables down again removing air bubbles. Move the jars to the refrigerator for storage up to 2-4 weeks.