You will need a fault line template for this. It is a trapezoidal prism- each side matches up at a slant to demonstrate plate movement. a trapezoidal prism is pretty crucial to this activity. A simple cube doesn't give as good of a visual.
The top of the box is decorated by students to show the earth's surface. Below the surface are three different layers of the crust. This bit is crucial to show what happens when plate move and how geologists are able to study plate movement based on how the layers are mismatched on each side of the fault. You can take this activity pretty far! Have students show strike slip and dip slip motion with their models. Have them observe and take notes as the go along. I love this activity!