This is a great way to visualize what happens when rock layers are folded and subject to subsequent weather, erosion, etc. The activity is based on this lesson.
You'll need four colors of play dough.
Flatten each color into a rectangle about 1 cm thick. Stack the layers on top of one another. This is a good time to review which is the oldest layer (the bottom) and which is the youngest (the top).
Push on two opposite ends of the play dough and watch your rock layers fold. What kind of fold did you make? (anticline)
Use a knife to slice some of the play dough off the top. Look down - What do you see? What do you think the layers look like on the inside?
Slice through the play dough rock layers and observe the cross section.
Place the two halves back together, slightly askew, and you can see what happens to rock layers at a strike-slip fault.