This lesson originated as an amalgamation of two projects I've taught to 3rd grade in the past. One of my goals was to create more 3D lessons this year. This was my attempt for 3rd grade.
Essentially what I wanted to do was have a paper landscape with individual pieces created for the foreground, middle ground, and background. The landscape would depict the habitat of an animal that would also be included in the work. The landscape elements would be combined with two accordion-like edges, and a little paper frame would finish the front. It would look something like this quick demo piece I did.
The project went great. Then I demonstrated how to put the whole thing together. That's when I got the dreaded look of confusion from most of the class. I knew the way I had it planned was going to be kind of difficult, so I had my demonstration broken down pretty well. I was using a document camera and my projector to project my demo on the big screen so everyone could see. We worked step by step. A few kids got it, but it was mass confusion for the rest. Needless to say, I changed things the next day.
I ended up making little springs out of 1x3 strips of card stock and having students attach attach several in between layers of their landscape. I still really like how the project turned out and it was MUCH simpler to teach to my other four classes.