Slight change of plan, the person who really wear the pants in our household (You know who im referring to :help decided we need to make it 35x15 instead of the previous 20x15 dimension. So below is what my other option entailed. Build a wood form around the perimeter. Screed with 2x4. Then bull float. No need to build any other wood forms ddown the middle as reference ? Does that sound good to go?