For this you will need\\
  * 2 rolls cheap toilet paper
  * 3/4 cup white glue
  * 3/4 cup joint compound
  * 2 tablespoons lineseed oil (optional)
  * white flour

Take the tissue paper out of it's rolls and soak it in water. Pull it apart into bits, then try to squeeze out most of the water. Add the white glue and joint compound (lineseed oil optional), then mix with an electric mixer with dough hook. To make the clay a bit firmer, add in white flour until you get a consistency. Add a bit of bleach if you worry about the clay souring.  
