My mother and I made this a tradition after our cousin taught us how to make it. This authentic dish is served over rice with every meal in Korea. This can be altered for a spicier version. Use a glass container and wax paper as this will discolor plastic and rust metal.
Cut the cabbage leaves into 2 inch long pieces. Spread 1/4 of the leaves into a large, non-metallic bowl and sprinkle with 1/4 of the salt. Repeat layering all of the cabbage has been salted. Let stand at room temperature until a lot of liquid has been pulled from the leaves and the cabbage is tender, 3 to 4 hours; drain. Rinse the cabbage in 2 or 3 changes of water. Drain again very well and return the cabbage to the mixing bowl.
Sprinkle the cabbage with the minced garlic, green onions, MSG, and red pepper flakes. Season to taste with additional salt and toss until evenly combined. Pack the mixture into a sterilized gallon-sized glass jar. Cover the jar with wax paper and a loose fitting lid so the seal is not airtight.
Allow the cabbage to ferment at room temperature until it reaches the desired degree of sourness, 2 to 5 days. Store in an airtight jar in the refrigerator.