Use a ruler to draw two diagonal lines from one corner to it's opposite corner.
Use the ruler to draw one horizontal line and one vertical line.
Draw 5 or 6 curved lines in one of the triangle "pie" shapes.
In the next triangle "pie" shape, draw 5 or 6 curved lines that are reversed.
Continue the curved lines. Be sure to reverse the curved lines as you go.
Trace over all the pencil lines with a thick black Sharpie marker. Erase all your pencil marks.
Use a black colored pencil to darken the horizontal, vertical and diagonal lines. Add some shading to each "pie" piece.