Remove the outer leaves of the cabbage and discard. Cut the cabbage into quarters, remove the core, and finely shred the cabbage using a knife or mandoline.

Place the shredded cabbage in a large bowl. Add the sea salt and massage the cabbage with your hands for 5-10 minutes, until it starts to release its juices.

Transfer the cabbage to a clean quart-sized mason jar. Pack it down firmly with your fist or a wooden spoon to release more juices. The cabbage should be fully submerged in its own brine. If not, add a little bit of filtered water.

Place a fermentation weight on top of the cabbage to keep it submerged below the brine. Make sure there is at least 1 inch of headspace between the weight and the top of the jar.

Cover the jar loosely with a lid and ring. Ferment at room temperature (65-75°F / 18-24°C) for 1-3 weeks, or until it reaches your desired sourness. Check daily and press down on the weight if needed to release any trapped gases. Taste after 7 days, and then every few days.

Once the sauerkraut is fermented to your liking, remove the weight and tighten the lid. Store in the refrigerator. The flavor will continue to develop over time. Enjoy!