Cut a circle out of paper, exactly the same size as your plywood circle
1. Cut a circle out of paper, exactly the same size as your plywood circle.
2. Place the paper circle on top of the plywood circle, with its center on the outside edge.
3. Draw an arc around the paper circle, on the plywood.
4. Move the center of the paper circle to the intersection of the arc and the edge of the plywood (there are two, just pick one).
5. Repeat until you've drawn 6 arcs with centers around the circumference of your plywood circle.
6. There are now six equidistant points around the circumference of your plywood circle. Pick three alternate points, and they will trisect the angle of 360 degrees.