Edited

I just cut the cabbage into very small pieces (kind of shorter strings), then I place it into a jar and fill the jar as much as possible, pressing the layers (apparently it has to be very well pressed - in my country of origin they used to be making it in a big wooden barrels and they were walking on the cabbage in those barrels to press it really well), so when the jar is full and all well pressed down, I fill the rest of the jar with salty distilled water (use as much or as little salt as you like, not over-do it, so it's not too salty), place a jar cover over it and let it sit in a warm place (I just keep it in the kitchen on the counter) - for few days; in the recipe I found they said 5 days but I have to keep it longer sometimes, probably depends on the room temperature - basically you keep it until it gets sour, then it's ready to eat and then only I keep it in the fridge so it doesn't get more "cultured". This is a natural process of culturing the cabbage, there is nothing else you need to add - it gets sour by it's own and it's supposed to be a healthy natural culture/probiotics.
Sometimes it gets tricky in how long it takes to get cultured=to get sour, and I still didn't figure out why would sometimes take less days and sometimes more days - but if you keep tasting it and at the moment when it's sour it's done. Tweet