Player 1: Thankfully this is another short chamber, so start off by shooting a portal on the square wall panel that’s on the left-hand wall (facing the square force field) and another portal at the ceiling where the excursion funnel stops. This’ll create a funnel that stretches out over the length of the chasm below.
Player 2: Jump into the funnel that player 1 kindly created and immediately fire a portal off into the wall panel directly ahead of you at the end of the funnel. Now as you approach the middle of the room, look to your right and - quickly - get a portal on this wall. Now step across to the middle funnel and when you’re high enough up, simply drop down into the horizontal funnel that leads to the exit. There’s a red button up on the ledge here, go stand by it now.
Player 1: Now for the cheeky shenanigans… step into the first portal you created on the wall and you’ll reappear as you float downwards (although you’ll swear you’re travel upwards) towards the start of the excursion funnel itself. Ask player 2 to step off the switch now, causing you to raise upwards. Now simply look for the horizontal funnel leading to the exit, step across into this and make your way to the next test chamber!