I use the Waking Up app. I don’t know if it meets the “proven claims” standard, but it presents a very intuitive framework. You are simply taking to time to notice the phenomenon of consciousness; the more time you spend in this state, the more nuanced it will become; and a guided meditation helps you stay on the tracks, so to speak, so that a fluency like that of language can develop naturally. I would be put off by anything more esoteric than Sam’s methodology.