To begin with, trace the lid twice onto contact paper. Then cut out the tracings and then the middle of the lid, leaving a rim around the cut out area.
Next, unpeel one piece of contact paper and put it onto the back of the lid, so that the sticky side appears through the cut-out. This is a good time to create a hanging loop too. Just loop a piece of string and place the ends under the contact paper, leaving the loop hanging out over the top edge.
Then reach into your designer ziploc bag of collage goodies and start to place things on the sticky surface:
Little hands that were not going to be able to resist pulling it off the window so that they could examine it more closely. Curious, adventurous little hands that are keeping me busy these days!