Before start make a few sketches to plan your painting how it look. Then draw the center of your design.
Paint a light wash over the paper. Then let the paper completely dry.
Paint another wash layer except the center design.
After the paper completely dry then draw another layer around the center design and paint another wash around the second layer.
Continue the step above to add more layer you want. Make sure the wash is dry before start next layer.
Finally it done. I only fill up five layer on my painting for the A4 size watercolor paper. You can add more layer if you have more large size of paper.
I had done on few different color and shape. Enjoy your art work as well ^^