Take half a head of cabbage, and cut it into three equal wedges. Green cabbage layers are very tight, and cutting them into smaller wedges will help the vinegar and hot water penetrate. Don’t wash the cabbage at this point; you can wash it after it’s pickled.
In a deep heat-proof bowl that’s just slightly larger than the cabbage, add the cabbage wedges and ginger slices. Pour the boiling water over it, making sure to cover all areas (this process lightly cooks the cabbage). Next, pour in the vinegar.
Weigh the cabbage down with a plate, making sure the wedges are submerged in the liquid. Cover with a large lid or plate, and leave it on the counter overnight. In the morning, transfer the bowl to the refrigerator until you are ready to cook it. Use within 3-4 days.