Player 1 : Set your portals on the panel above the Arial Faith Plate and then on the slanted panel behind you to your right.
Player 1 : Step onto the Arial Faith Plate and you'll end up on the upper platform, which has a slanted panel on your left. Place the portal that was on the previous slanted wall here and ask player 2 to stand on the Arial Faith Plate.
Player 2 : Once player 1 is by the red switch, replace the portal over the Arial Faith Plate with one of your own, then set another one on the horizontal panel just under the platform that's holding the Companion Cube. Now hit the Faith Plate and aim yourself and as you're ascending, grab the Cube from the platform and take it over to player 1 who's still on the upper ledge.
Player 1 : It's Arial Faith Plate time again! So get a portal above the plate and then on the same horizontal wall panel that player 2 just used to reach the force field area. Hit the plate and you'll zip though all four portals and land right near the exit.
Now simply set a portal on the wall panel up by the exit and then on the horizontal floor panel on the floor.
Player 2 : Step through the floor panel and you'll join player 1 by the exit.