Photocopy and enlarge a U.S. Geological Survey topographic map of the desired landform
to the size you want, making as many copies as are index contour lines. Use a light setting to enhance the visibility of the dark contour lines.
Cut around the outermost contour line -- lowest elevation -- on one map copy, and label it #1. For each succeeding map copy, move in one contour line, cut around the contour line and number it.
Glue each contour line piece to corrugated cardboard using a glue stick.
Cut each piece of cardboard around the contour line.
Place the cardboard piece labeled #1 on the plywood base. This layer is the first one for the model.
Cut small rectangles of an expanded rigid polystyrene plastic for spacers between the layers. Remember to maintain the scale of your landform model.
Adhere the needed number of spacers, using the glue gun, to create the elevation between the base and the second layer.
Fill in the area inside the spacers with modeling clay or papier-mache.
Glue the second layer to the top of the expanded rigid polystyrene plastic spacers, and repeat the process with the remaining layers.
Add modeling clay or papier-mache to the model as needed to make the landform look realistic. Pay attention to whether the distance between layers has a steep or gradual incline.
Place optional pieces on or around the landform. If you used papier-mache for the model, then allow it to dry before painting it and placing optional pieces.