When reversing directions for reassembly, the logic board needs to be clipped into the clips on the side.
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Although I would say "needs to be slipped under the clips on the side". The most obvious clip is next to the camera, facing south (if the camera is in the NE corner). There is a corresponding clip on the opposite side of the north end the logic board, facing east (a bit east of the #6 ribbon cable).
It's still possible to get all the screws back in with the logic board above the clips (trust me), but it's a serious barnus because the SIM card holder won't fit back in and the camera will be pointing a bit askew ... and you'll have to pull all the screws back out and figure out what you did wrong (and why you had a naggling suspicion the logic board wasn't placed quite right).
I would recommend sliding in the SIM card tray *before* putting any screws back, just to make sure.