I recently made a show box and I used styrofoam from michaels
Here it is http://iheartcutecupcakes.blogspot.com/2013/06/louboutin-shoebox-cake-w-red-bottoms.html
I then applied piping gel and then covered with fondant. So when it was time to cut the cake all the customer had to do was remove the top. And it is very light weight and it looks real.
