When I was a kid, my mom helped me make one for a fifth grade class project. We bought some brown clay from Micheal's craft store and shaped in into a cone and hollowed out a long tube in the middle. We poured baking soda in it and then decorated a plastic box lid with green felt and plastic dinosaurs. We added red food coloring to some vinegar and then when I got to school, I poured the vinegar in, and voila! Simple and easy volcano. Because it was on a box lid, the edges of the lid prevented a mess and the felt absorbed a lot of the liquid as well.