Cut the cabbage into 2-inch pieces and place in a large bowl. Sprinkle with the salt and massage it into the cabbage until it begins to soften.
In a small bowl, mix together the red pepper flakes, garlic and ginger. Massage this mixture into the cabbage until it is evenly distributed.
Pack the mixture into a jar or crock and press down firmly so that all of the ingredients are submerged in their own juices. Cover with a lid or cheesecloth and let sit at room temperature for 3 days.
After 3 days, taste the kimchi. If it is too salty for your taste, rinse with cold water before serving.
Store in an airtight container in the refrigerator for up to 1 month.