My meetings are all in conference rooms. What happens to the room if I mark the meeting as flexible?

Clockwise will let you select if you prefer to meet in the same room, or if you are willing to switch to a similar room.  If you select Keep original room, Clockwise will only move the meeting to a time when that room is available.  If you select Ok to move to similar room, then Clockwise will use your past meeting rooms and the average number of attendees in those rooms to identify similar conference rooms to the one you chose.