We were looking through a kids' activity idea book and found this one: keeping flowers inside contact paper.
We cut two sheets of contact paper to the same size, then cut a piece of construction paper as the frame. We could have decorated it at this point.
Then we opened one piece of paper, put the frame on it, put some flower petals inside, and a few leaves, then the other sheet of paper on top made a sandwich.
To hang it, we used a hole punch and ribbon, and hung it in the window. I think it turned out really nicely.