I used needlenose pliers and the T10 to align the screw into the hole. Otherwise the screw keeps jumping to the magnet. And patience with this NON-CAPTIVE screw design (c’mon Apple, even **I** came up with that, and I’m an idiot!)
Take a moment to clean off any crud from around the perimeter ring of the home button. Use a sewing needle for its sharpness to CAREFULLY pick away any debris. Makes a clean assembly for when re-assembling the button back into a new display module.
Watch orientation of iMac in relation to this picture: if the base is AWAY from you, the screw positions are reversed in this picture. Also use the black power cable for position reference.