In a large bowl, combine the cabbage, carrots, and garlic (if using). Sprinkle on the sea salt. 

Using clean hands, massage the vegetables for 2-15 minutes, or until the vegetables are shiny and soft, and there is a decent amount of liquid in the bottom of the bowl. When you pick up a handful of the mixture, liquid should stream out. Alternatively, massage the salt with the vegetables for two minutes, then let the mixture rest for 20-30 minutes, then come back to massage for an additional minute or two. 

Working one handful at a time, pack the sauerkraut into the mason jar, using your fist to tamp the cabbage in tightly. Continue to do this until the jar is 75-85% full. There should be quite a bit of liquid by the time the jar is filled.

Top off the jar with additional brine from the massaging bowl. Then submerge the cabbage in the brine by following one of the methods listed in the post. 

Close the jar, either with an airlock lid or a regular lid, and set in a room temperature (65-70°F) spot out of direct sunlight to ferment. If using a regular jar, “burp” the jar each day by just sightly unscrewing the lid. 

Check the sauerkraut for flavor starting on day four and taste every day or two until it achieves the texture and tang you prefer—anywhere from 4-30 days. 

Store the sauerkraut in a jar in the fridge for up to six months.