Clean out a clear container with soap and water. A container that you can see through is ideal to observe the behavior of the worms. A large glass jar or a large soda bottle with the label removed and the neck cut off both work for a compact wormery. For a larger project, use a fish tank.
Place a layer of sand at the bottom of the container about 1 centimeter deep. Follow with a layer of soil. Continue to alternate layers until the highest layer is about 2 inches away from the top. Home Science Tools suggests that using two different types of soil will build an even better wormery.
Place organic material on top of the sand and soil layers. Dead leaves along with kitchen scraps such as coffee grounds or tea leaves, vegetable peelings, and eggshells will provide food for the worms and give them a job to do. In "Making a Wormery," The Kids Garden states that worms dislike citrus peels, onions, fish or meat.
Add earthworms. Earthworms can easily be found in a moist area, such as in a yard after it rains or under rocks near a creek. Kids will enjoy the task of searching out the worms, but they can also be purchased at a bait store if necessary.
Cover the container with dark paper and place in a cool place. Earthworms like a dark environment and they must stay moist to breathe. Place paper or cardboard over the top, poke some holes for oxygen and keep it out of direct sunlight. Every few days, observe the wormery to see how it has changed.