First you will need some Watercolor paper (we used larger pieces and I cut them down to 12x12 inches)
Oil Pastels (we used Crayola's brand and they worked great) note you can use regular wax
crayons but I think the oil pastels are more fun.
Watercolor paints (I have a few and honestly can't remember which ones we used for this project)
A flat watercolor brush or other brush that you like
A ruler (What you say Math? Yes sneaking in a little math never hurts)
Now that you have all your materials out take your paper and divide it into 9 equal squares by measuring off every 4 inches both vertically and horizontally and then use your ruler to make your straight lines dividing your 9 squares. You could sneak in some measuring skills and fractions too. Thinking about it there are arrays also.