Take the lid off of a shoe box and discard it. Place the bottom portion of the shoe box onto a table top or desk.
Press air-drying clay inside of the shoe box, leaving a 4-inch path down the length of the box uncovered. Form the clay into hills and valley so that it resembles land. Allow the clay to dry for 1 hour.
Paint the clay land using brown and green acrylic paint. Dab the paint onto the land in a random, splotchy pattern, covering all of the land completely. Allow the paint to dry for 20 minutes.
Paint a 4-inch strip down the middle of the box, in between the land forms, using medium blue acrylic paint. This will represent the river in the diorama where the beaver dam will exist. Allow the paint to dry for 20 more minutes.
Paint a layer of clear acrylic glaze over the blue river, then sprinkle clear microglitter over the wet paint. This will make the river look as if it is wet and sparkling. Allow the glaze to dry for 30 minutes, then shake off the excess microglitter.
Arrange the box so that the river is running horizontally, then apply a 1-inch wide vertical strip of clear tacky glue over the river. Press pieces of straw or raffia over the glue, covering it completely. Allow the glue to dry for 15 minutes, then cover the straw with another layer of glue and straw or raffia. Allow the glue to dry for an additional 15 minutes. This will represent the beaver's dam across the river.
Cover the painted land form with tacky glue and press dried moss onto the glue. This will make the land look more realistic. Allow the glue to dry for 15 minutes.
Squeeze tacky glue onto the bottom of a small, plastic beaver figurine, then press the beaver onto the diorama where it will be working on the dam. Allow the glue to dry for 15 minutes before displaying the beaver diorama.