Prep the cabbage. Begin by rinsing the cabbage and discarding any wilted outer leaves of the cabbage.
Quarter the cabbage by using a sharp knife. Remove the core and then slice the cabbage into thin strips, aiming for approximately ¼ inch in width. The strips don't have to be perfectly uniform. If you prefer you can also use shredded cabbage. Transfer the sliced cabbage into a large bowl and evenly sprinkle sea salt.
Mash the cabbage. Now, initiate the mashing process. There's no specific technique; the best way is to use clean hands and massage the cabbage. The objective is to kickstart the release of juices from the cabbage. Continue mashing or kneading for about 5-8 minutes. By the end, you should have a pool of salty cabbage juice in your bowl as the salt draws juices from the cabbage.
Take a few handfuls of the mashed cabbage and place them in a glass jar, then compress them thoroughly using a wooden spoon. The goal is to remove as many air bubbles as possible. Repeat this process of packing and mashing in small batches until the jar is nearly full, but leave approximately 1-2-inch headspace at the top. If the cabbage is not fully submerged in its liquid, prepare a 2% brine solution to fill the remaining space. (Failing to cover the cabbage fully may lead to mold and other issues.)

Tips

Check the cabbage daily to ensure it has enough liquid to ferment in so it can create good bacteria and produce good sauerkraut.
Taste after 5 days. If the cabbage tastes to your liking, transfer it to the refrigerator for 3-6 months. If not, allow it to ferment for another 2 days and then taste again. The longer the cabbage is fermenting, the sharper the flavor. There's no fixed minimum or maximum fermentation time; it's safe to eat throughout the process.

You may end up with some exposed sauerkraut at the top of the jar that looks like it went off. Throw it away, but if the rest of the jar looks okay, it’s fine to eat it.

Optional ways to season Sauerkraut

Basic Sauerkraut