On my HP EliteBook 840 G5, the “two side screws” (black) are found inside the two holes seen next to the left top screw, and between the center and right top screw.

Great guide, thanks so much! Regarding step 1: On my HP EliteBook 840 G5, the two “side screws” (black) are found inside the two little holes between the center one and the outer ones of the “top three screws”.