Washed and sliced ginger can be peeled or not. Add salt and marinate for half an hour, rinse with cold water, drain the water, and put in a glass container. Add rock sugar and vinegar. Put it in a cool place for a week.
The longer the curing time, the better the taste. Some people boil the vinegar and sugar. I never cook it. But I need the ginger to be fresh. To dye the next three dried roselles, after the coloring, It is taken out to avoid vinegar and water.