How is Meth manufactured?

It is made illegally. The question is poorly thought out, which makes for a poor answer. Asking how to make Meth is like asking how to make brownies. There are thousands of ways to make brownies my granny used to make them from scratch, but some people buy the mix at the store. So you see their is no real or exact science and just like brownies every batch is a little different, that's why grannies brownies don't taste like store bought brownies Meth is not a pure drug there's literally thousands of types of Meth. The best analogy I can think of is making Meth is like painting, everybody starts with the same ingredients and supplies like brushes, paint, canvas, but what truly makes the painting any good or have any value depends on the experience and abilities of the painter. No one can be told how to paint a picture like no one can tell you how to make Meth you have to be shown the process.