I had so much fun making my demonstration box that I want to keep it!
only problem is, like I've mentioned I live in 300sq feet and it is filling up with "art projects" :/
What you do is cut a square out of the front of a cereal box to make the frame for your shadow box.
Then on the piece of cardboard that you cut out you start gluing magazine scraps to make a scene. I think it looks better when some of the pieces stick out to make it look 3D, like the grass.
An underwater scene would be awesome don't you think?
and it's a free, recyclable craft you can do with your kids :)