These boxes are really easy to fold (and I mean it - really easy). So I was so expired, that I made even two advent calendars: one for work and one for home. First our advent calendar in the office. I've folded the boxes and brough them to work last week on Monday. Each colleague in my team took two or three ones to fill. On Friday, when everyone was done, we decorated the boxes and put numbers on them. Another colleague made some small papers with our names, so every day we draw one of them and this person gets the box of the day :-) It is really fun, as no one knows first what is inside and who put it there.
So colleagues put a lot of effort something in there :-)