3D Optics
Make your own 3D pictures and view them.
Any colored chalk will do- but avoid white.
You can get these glasses cheap (less tha 1$) online. Be sure they are the kind that work with Crayola 3D chalk (there are many types of 3D glasses)- and shop around. There’s wide variability in price.
3D Optics Powerpoint Courtesy Janelle Shane, University of California San Diego