The box is an imaginary object. When somebody has been smoking weed/head shop and it is too much for them they start to get on a 'bad buzz' and this leads to them 'greening out'. In the event of this, the person can be sent further into the 'bad buzz' by freaking them out and messing with their head. By pretending to place an invisible box over them and everybody continuing as normal but silently, the person feels shut out (or in) from the rest of the world as they can see everything going on but cannot hear. Even when the person 'in the box' starts freaking out and trying to get peoples attention, nobody takes notice or acts differently which makes the person even worse as they really have no idea whats going on.
Human1: I was with ''Jerry'' the other day smoking a blunt and he started 'greening out'.
Human2: Yes, he often does that, what happened?
Human1: I put him in 'The Box' and he got sick after 2 minutes
Human2: Haha, you must have really got him good