Select a work area that is easy to clean up and where your volcano can sit for a few days. Cover your work space with the newspaper.
Place the piece of cardboard inside the cookie sheet, trimming the sides to fit. This will serve as the base for your volcano.
Create a wide opening for the lava by cutting the neck off the soda bottle at a slight angle. Glue the bottle to the cardboard, and let dry for at least one hour. Once dry, add the vinegar, detergent and food coloring to the soda bottle.
While waiting for the base of the volcano to dry, you can prepare the modeling clay by mixing the flour and salt. Add water and knead until you have a thick, clay-like consistency. Handle the clay as little as possible.
Construct the volcano with the clay, using the soda bottle to keep the volcano's form. The base should be the widest point, and the top of the volcano narrow. If you need to mix another batch of clay to finish the volcano, be sure the existing clay on the volcano has dried sufficiently. For durable results, let the clay dry overnight.
Once the volcano is completely dry, you can begin painting the clay. Use traditional colors like brown for the volcano and green for the trees at the base, or get creative and use any color that comes to mind.
Once the volcano has dried, you can plan the eruption. Place the baking soda in the middle of the tissue, and twist the sides closed to create a ball. Dropping the baking soda into the volcano will begin the eruption. Stand back, and watch!