I'm not entirely sure either. The edges (flaps?) on my square piece were actually folded back, but like I said, the whole thing was just floating freely. Your picture got me thinking that maybe it was intended to sit in the middle (flat side down, flaps up) with the flaps somehow going under the side flaps? Dunno. Don't have the box with me right now to mess around with it either.

It's a puzzle for sure.