Weigh your cabbage to see how much salt you should use.Remove the outer leaves of your cabbage and any that are damaged. Discard. Cut out the core and rinse the cabbage well, allowing the water to flow between the cabbage leaves. Drain well.Reserve 1 outer leaf. Thinly shred the remaining cabbage with a knife or food processor. Place in a large bowl. Sprinkle the calculated amount of salt over the cabbage and toss well. Let sit for 15 minutes. Massage the cabbage with your hands for 5 minutes. The cabbage should release a good amount of liquid during this time.Pack the cabbage firmly into a very clean glass quart jar. Pour the liquid that was released during kneading on top. Cut a circle the same diameter as your jar out of the reserved cabbage leaf. Place it on top of the packed-down cabbage. Place a weight on top of the cabbage to ensure that it stays under the brine. If the brine doesn't completely cover the cabbage and weight, top off with a 2% solution of salt water (1 teaspoon salt per cup of water).Screw a plastic lid onto the jar. Place the jar in a rimmed pan (to catch any overflow) and allow to ferment at room temperature until the kraut is as sour as you like it. This can take anywhere from 1–4 weeks.After it's done fermenting, store the sauerkraut in the refrigerator.