DIY Photography with Larry Becker: Light Stand Wheels
Draw an equilateral triangle on your plywood, then find and mark the midpoint on each side of the triangle, and draw a straight pencil line from each corner to the midpoint on each side. Measure 1.5″ on either side of each line and draw a parallel line. This should give you guidelines for cutting out 3″-wide legs from your triangle. I used my circular saw to do this.