Place cabbage in a very large bowl. Mix together sea salt and water and stir until sea salt has dissolved. Pour over cabbage and mix together with your hands. Let sit for 1.5-2 hours.

In the meantime, blend together onion and garlic with ¼ cup water to create a puree. Pour into a medium bowl then mix together with Doenjang, red pepper powder, and green onions. If you are making a separate radish kimchi, save a bit of this mixture for the radish kimchi.

Once the cabbage has significantly wilted, rinse cabbage to get most of the salt water off. Place back into the very large bowl then toss the cabbage with the red pepper seasoning mixture until well-coated.

Place seasoned kimchi into a large mason jar and using your fist, punch down the cabbage to compress it all in the jar. Keep stuffing the jar until it is completely full and use another jar, if needed.

. Tightly close the lid on the mason jar(s) and leave out at room temperature overnight. Taste the kimchi the next day and if you prefer to have it more sour, leave out for another day or more. If you think it tastes fine after it has sat out overnight the first night, place in the fridge.

. Alternatively, if you have one, you can use a fermentation crock. Pack kimchi mixture into crock, assuring that all cabbage is submerged in the liquid. Add a small amount of water if needed to submerge cabbage. Using a crock weight helps ensure the cabbage is submerged. Ferment at room temperature for at least one day, or longer if you like a "funkier" kimchi (I do 7 days). Remove kimchi from crock and pack into mason jars, mark with packing date and store in fridge.

Kimchi can last for a very long time in the fridge because it is a fermented dish. I would say probably no more than one year though, but that's just me...