This is a great little lesson plan for getting younger students excited about learning their biomes. Here is a small summary of the procedure and a link to the site with the full lesson plan.
To build this model-biome students should bring with them a box of at least 1 foot by 1 foot and construct a biome within it. Inside the box the students should put representative plants and animals. They should show the terrain of the land (ie. mountains, streams or underwater terrain). The inside can be painted and decorated as they please. The outside of the box should display the following material: