I recently got my copy of The 4-Hour Chef in the mail and I have yet to put it down. There are many sections in the book, most related to cooking (hence the title). But there is also a good portion of content on "hacks" for everyday things. I have just broken into the "Scientific" section and the first thing I'm testing out is Fermentation.
The formula is very simple. Cabbage + Salt + 6 days = Sauerkraut. It is created by a process of pickling call lacto-fermentation. This is caused naturally by the bacteria that culture naturally on raw cabbage leaves when they are grown.
I've posted a few photos below of my day 1 set up. I plan on checking it daily and taking a new photo to show the change. I've read that I may have to discard the top layer as it molds/spoils.