After they get their weed the first time from the clinic they give some to the guy on the couch. He rolls over to take a hit and then rolls back over. Throughout the scene he is shown with his back to everyone. Then when he is about to start flying he is shown facing out.
Well, the thing is we don't see him in the cameras view so he probably just rolled over. Common sense. Just because you don't see him doesn't mean he stops until he is shown again.
Actually you're completely wrong, After he takes a hit he stays on his side with his face towards the coffee table, Watch the movie then try again there slick