Cut yellow poster board into large oval shapes about 1 foot high by 4 inches wide. Cut one oval for every corn stalk needed.
Draw corn kernels onto the poster board ovals using a brown marker. Draw rows of small, rounded squares until the surface of the ovals are completely covered. This will create the cob of the corn stalk.
Use a hot glue gun to add pieces of straw to the cob to create the look of corn silk. Do not add too much straw, as this will overpower the corncob.
Cut three pieces of natural-colored raffia paper into strips measuring 1 1/2 feet long by 5 inches wide. Raffia paper can be found at craft stores. Scrunch the raffia paper to create a wrinkled corn husk effect. Using a hot glue gun, glue the raffia paper to the base of the the paper corncob. Glue one piece of raffia paper to each side of the cob, and another piece to the back. This will create the illusion that the cob is growing out of the husks.
Tape the corncobs to wooden dowels or bamboo stems using heavy-duty tape like duct tape or masking tape. This will create tall corn stalks. Wooden dowels and bamboo shoots can be found at home and garden centers.
Push the wooden dowels or bamboo shoots into blocks of Styrofoam. Use large pieces of Styrofoam measuring approximately 4 feet long by 1 foot high by 1 foot wide. This will create a light base that is easily moved when set changes occur. Place several corn stalks into one piece of foam to create the corn field effect found in the Wizard of Oz. Creating several foam bases filled with corn stalks may be necessary to achieve a full-looking corn field. Attach long pieces of string to the foam bases for a quick retrieval method when the corn stalks need to removed for the next scene.