I was watching a video on how to install the Noctua NH-D14 and the person flipped his motherboard and just placed it down on the table. I am wondering is this safe to do? I would assume that this would warp the board
Well, I wouldn't set a 25 pound bag of sugar on it, or do anything to put a lot of force on the board, you wouldn't want to to that no matter what the orientation of the board is. But turning it over and working on it from the back should not be a problem.