The Boardroom is found shortly after defeating Black Cerberus in the Executive Forum area.
You will come to an area with a large staircase protected by 2 Cerberus guards. However the Door to the Boardroom is locked. To the side of the large stairs is a door head through use the lift and enter the server room.
Once here Overcharge the panel. Before leaving inspect one of the computers to unlock the meet Sally achievement.
Overcharge the panel will unlock the Boardroom door.
Dispatch the guards and enter. Walk into the holographic visuals to initiate a cutscene with Sally and unlock the achievement.