First, understand that an altered state of consciousness is also a way of saying hypnosis or deep meditation. You can do this naturally with meditation or self-hypnosis. As a writer, when uninterrupted at my keyboard, I naturally go into an eyes-open altered state. But I don't nearly as deep as when I'm using an electronic program or doing self-hypnosis. Long-distance runners usually go into an altered state after running about one mile.
Artists go into an altered state while working.
So do many of you reading this. If you experience an activity that allows you to totally focus and time seems to disappear, you're naturally altering consciousness in the process. You may have had the experience of someone talking to you while you were watching TV and you didn't hear them. You probably figured that you were just engrossed in the program. But an altered state so totally focuses your attention upon one thing, that you tune everything else out.