Research your assigned topic thoroughly. Draw a sketch of your proposed diorama to use as a guide. Select the appropriate colors and textures for your diorama's background and determine which figures you will need to make to add authentic details to the scene.
Paint the inside walls of the box in colors appropriate for your diorama theme -- blue for sky, white for an Arctic landscape, or sandstone cliffs for the Anasazi Indians, for example. Allow paint to dry completely for one to two hours.
Paint additional background items on the back wall of the diorama. Paint the floor to look like the ground of your scene. A diorama of the Antarctic might have a white floor, the rainforest might be covered with green plants and vines and the old American West would be painted to look like a dusty patch of ground with some rocks scattered about. Allow paint to dry for one hour.
Make figures from modeling clay or other craft supplies to add details to your diorama. Build trees with brown pipe cleaner trunks and green tissue paper leaves. Make icebergs or snow out of white sugar, styrofoam or crumpled white tissue. Modeling clay is perfect to make people or animals; small plastic figures may also be used populate your scene. Glue the trees, dinosaurs, mountains or colonists firmly to the appropriate surface of your diorama.
Add the final touches to your diorama using craft miniatures, beads, metallic embellishments or textured papers. Small doll house baskets add detail to a Native American scene. Colored beads can represent a field of flowers or fruit in the trees. Use blue cellophane to make bodies of water and silver sequins as stars. Fine-grain sandpaper makes a realistic-looking sand floor for an Egyptian desert scene or the sides of a pyramid. Glue all items carefully to the floor or walls of your diorama.