Chapter 2 Chamber 6. When you get to the button to release a cube when you first press it glados will drop a load of crap out of it including a radio and a turret required for these trophies-
so do those trophies first!
Now that you've gotten those two out of the way put your first portal on the first light grey slope and the other on the ceiling above the button that activates the door. You've now moved cube to button without touching it! Trophy unlocked