the board and mark it on the plastic with a marker, all the way around the base. this is just to trim the plastic to be easier to work with. see picture 4. trim off the excess by following this 6" line with a pair of scissors, it should look like picture 5.
now fold the plastic up over the top of the board and pull it tight. it is nice to have someone hold the plastic while you measure. measure four inches from the edge of the board and mark it on the plastic with a marker. see picture 6 for reference. you need to do this around the entire 