The final step is to cut and attach the plastic sheet to the wooden base. Our plastic was thin enough to be cut with a utility knife, but you may need to use more agressive tools if you are using thicker plastic. Size the plastic so that it fits evenly on the base. You can use the edge of a sharp blade to scrape the edges of the plastic to create a good finish. Glue the plastic sheet in place and then pour your washers to complete the project.