Remove one or two outer leaves from the cabbage and set aside.
Cut the cabbage in half and remove the core.
Thinly slice the cabbage.
Place in a bowl on a scale and weigh the cabbage.
Add salt. 1 teaspoon of salt per pound of cabbage.
Massage salt into shredded cabbage. Squeezing firmly.
Continue to do this until the cabbage is releasing it's juices. If it's taking too long you can cover the bowl with a towel and let it rest for 15 minutes or so and try again.
Pack tightly into a jar or crock.
Top with with the reserved cabbage leaf and press down until everything is submerged.
Add a weight or spring to hold everything down under the brine.
Cover with a breathable lid, like the one that comes with the lid and spring set or a cloth and rubber band will do.
Leave to ferment in a cool dark place for 15 days or much more. It's up to you.
Notes
The sauerkraut is done when it tastes good to you. The longer it goes, the softer, darker and funkier it will get. I prefer my kraut at about 18 days. A lighter color and tangy yet crisp.The hotter it is in your house the faster the ferment will develop.Be sure to skim off any foam and remove any bits of cabbage from the surface of the jar so you can avoid growing mold.