Remove any damaged outer leaves. Core the cabbage and cut into thin slices.
Place shredded cabbage and salt into a large mixing bowl. Let ingredients sit for several minutes until the cabbage softens and begins to release water.
Using your hands, knead the cabbage to release it's liquid into the bowl. Do this until the cabbage is no longer stiff and there is a enough liquid in the bowl to cover the cabbage when transferred into the mason jar. This will take approximately 5-10 minutes.
Transfer sauerkraut into mason jars and tightly pack it down. Make sure all of the cabbage is covered in the brine.
Add a glass fermentation weight into the top of the mason jar to keep the sauerkraut submerged in the liquid. Place the fermenting lid on the mason jar and use the oxygen extractor to pull out any remaining oxygen from the jar.
Store your mason jar in a dark place (I use a kitchen cupboard) for anywhere from 3 days to several months. Ideally, the room temperature should remain between 65°F-75°F. The longer you let it ferment, the more sour it becomes. When it has reached your desired flavor, place in the refrigerator for long-term storage for up to 6 months.