By eliminating everything that is not the self.

Consciousness is always present. The problem is that ideas, beliefs, attachments, memories, senses, etc., obscure this fact. Therefore, if all such things are removed then consciousness prevails as the mind clarifies. If you can keep all thought only on the sense of "I am," then the other thoughts stop occurring. This is not something most people have a desire to do, because they find it unnecessary, unimportant or even scary. Anything that threatens the predominance of the self is defended by the self.