This is actually very simple, but it is more troublesome to do. Are you from Wuwei? My family used to make it by itself. That is, mix flour to make dough, and then put the dough in clear water (water should be appropriate) to wash the dough. At the end of washing, one piece of flour can't be washed out and melted, and that piece of flour is gluten. Then put the washed flour water into the roll and the gluten into the roll. Like steamed bread, steamed for a period of time, cooked, flour and water solidified, that is, dough, and the other is stool. This is the indigenous method made by my own family. Interested parties can discuss it together. I am from Wuwei!