Rather than using flat plate, I built mine from a piece of ten inch pipe, 4 feet long. I made a mark to start my cut, then on opposite end of, I marked four inches further around. I then cut a line from one mark to the other. I made another (one for each side). I the laid a flat plate across connecting the two sides, with the front of the plate raised to force the soil under it. The reason for spiral cutting pipe for the sides is make the soil roll to the center, and it is easier to tow. I posted some photos of it last year on another thread.