Directions
| 1 |
| Use a pencil to mark off four equal sections on each 91 cm by 30 cm (36 in. by 12 in.) piece of foam board. |
| 2 |
| Cover the first section with acetate sheets to create a slick surface. |
| 3 |
| Glue 3 small rocks across the middle of the plain foam of the second section. |
| 4 |
| Cover the third section with a piece of hessian or 3 to 4 sheets of cheesecloth. |
| 5 |
| Glue 10 to 12 small rocks on the plain foam of the fourth section. |