My DD has been on a roll with this simple craft. She's made 3 or 4 of these and I love them in our windows!
Gather a variety of colored fall leaves. Arrange on a piece of waxed paper (waxy side up) in random order. Place another piece of waxed paper on top, waxy side down. Gently ron with a an iron set on low/medium setting (just below steam setting) until waxed paper "melts" together. Let cool, then "frame" with a mat made from posterboard. DD glues the waxed paper to the back of the posterboard mat. Let dry.