In a large bowl, mix the shredded cabbage with the salt and caraway seeds (if using). Let the mixture rest for 15-20 minutes to allow the salt to start drawing moisture out of the cabbage. You can speed up the process by massaging the cabbage with your hands for 5-10 minutes.

Wash a quart sized mason jar well with hot soapy water. Pack the salted cabbage mixture and juices into the clean jar. Press the cabbage with the back end of a wooden spoon to pack it tightly and to remove any air pockets.

Place a quart-sized resealable freezer bag into the jar. Fill the bag with water and tightly seal the bag. This will act as a weight and will help to keep all of the cabbage submerged. Cover the jar with a towel, cheesecloth, or coffee filter.

Check the sauerkraut after 24 hours. If the cabbage is not entirely submerged in brine, add a saltwater mixture of 1 tsp salt to 1 cup water to the cabbage, just until the cabbage is submerged.

Place the jar away from direct sunlight to ferment. As noted above, fermentation can take anywhere from 1-3 weeks depending on the temperature and the flavor you want. Taste the sauerkraut every few days. When it reaches the flavor you want, remove the bag of water and cover the jar with an airtight lid. Store the sauerkraut in the fridge.