A description of the problem from wikipedia:
The origins of the phrase "thinking outside the box" are obscure; but it was popularized in part because of a nine-dot puzzle, which John Adair claims to have introduced in 1969.[2] Management consultant Mike Vance has claimed that the use of the nine-dot puzzle in consultancy circles stems from the corporate culture of the Walt Disney Company, where the puzzle was used in-house.[3]
The puzzle proposed an intellectual challengeto connect the dots by drawing four straight, continuous lines that pass through each of the nine dots, and never lifting the pencil from the paper. ...

My experience with this phrase was that it came from the corporate concept of TQM (Total Quality Management). They used the puzzle as descibed in the excerpt from wikipedia. I think that anyone who worked for a corporation in the 1980s went through some form of this TQM training. The original puzzle is an effective educational tool.
However, by, say, 2005, every corporate project that I worked on would start with a
kickoff where all the project bigwigs would get up and talk. I used to try to get people to bet me on what the minimal number of times any speaker would urge us to
think outside the box. 10 was a pretty safe bet - i.e. each speaker would say it at least 10 times.
In my experience, the words became a meaningless cliche. I can see how the suggestion here, to have people actually do something like step outside of a physical box and think, could restore some meaning to the phrase.