Conceiving a diorama is an adventure in scale and spatial relationships. Choose a container, then put yourself in the shoes of one of its future inhabitants.
Martha Stewart Kids, Volume 7 2003
To make the snowy scene, trace a well-washed ham can onto a piece of 1/2-inch-thick Styrofoam (an old cooler works well) five times. A grown-up should use a kitchen knife to cut slope shapes: The background layer should be full size; cut increasingly lower slopes from the other layers.
Glue in place. Cut bump chenille stems (fancy pipe cleaners) to make trees, trimming bristles off of bottom 1/4 inch of each for a trunk. To dust trees with snow, brush on white glue and sprinkle with borax, or spatter on white paint.
Poke trees into foam. Glue figurines, from a model-train store, into position. Stretch plastic wrap over the container, and secure with a white rubber band.
Using a toothbrush, spatter the plastic wrap with white paint for snow.