Cut the cabbage in half and slice finely.
Put half the sliced cabbage in a bowl and add ½ Tablespoon sea salt.
Using your hands, begin squeezing the cabbage. You want the cabbage to begin breaking down. It will appear that the cabbage is starting to wilt.
Add the other half of the cabbage and ½ Tablespoon sea salt. Continue squeezing the cabbage until the leaves are wilted and moisture begins to drip off the cabbage.
When a briny liquid has been achieved, pack the cabbage into a clean Mason jar. Push the cabbage down hard to remove most of the extra space.
Set a small 4 ounce Mason jar inside the larger jar on top of the cabbage. This will help weight the cabbage down.
If your cabbage contained enough moisture, you should have liquid covering the cabbage completely. This is essential because you want to submerge the cabbage in brine (for the anaerobic environment). If there is not enough liquid, add some salt water until the cabbage is completely submerged. To do this, mix 1 cup of water with 1 teaspoon sea salt.
Cover the uncapped mason jar with a kitchen towel and set in location at room temperature, out of direct sunlight. I keep mine on the counter top so I remember to check on it.
For the first few days, check on the cabbage and add extra liquid to keep the cabbage submerged. A bit of white foaminess is normal. You will notice the cabbage lose its bright green color as well. Do not dismay! However, be on the lookout for anything that looks discolored or moldy.
Taste your sauerkraut after about a week. It will probably taste a bit tangy but will need more time. I live in Southern California (read: pretty warm) and find it takes about 10 days to get to the flavor I like. The length of time will vary depending on the ambient temperature.
When finished, store covered in the refrigerator and enjoy often.