Turns out that wasn't so easy.
Via the "Improv Everywhere" video description:
For our latest mission, a group of 24 actors between the ages of 48 and 78 staged an unauthorized boardroom meeting in the office chair department of a Staples. The chairs in this particular office supply store were already arranged in a boardroom configuration, making it easy for us to hold a surprise meeting. Actor Will Hines gave a presentation to the board, using a whiteboard and an easel he had bought from the store just minutes prior. Minutes into the meeting, the board was asked to leave by a confused store manager.
Looks like there is a reason Staples has so many office chairs after all. Great to see them being put to such practical use.