He's implying that Verton laying on his side will cause the dream to tilt, like in Inception.
However, Verton is already laying down in the real world, so his current inner ear sense of balance is actually oriented to be on his side.
If you could get to Soren in the real world and tell him to prop Verton up so he's standing, you could, in theory, do what FancyPants said.