Quick and easy!!!!
We go to the beach as it is within walking distance. Students sticks their hands into the moist sand.
Some make signs with their hands, some just spread their fingers, no obscene jesters allowed. I then pour plaster into their sand molds. Within 20 minutes the plaster is hardened and students gently lift up thier castings. Always a favorite project. Could be adapted to the class by filling shoe boxes with sand to make molds in the class.