Emboss watercolor or other non coated paper in an embossing folder and run through a Cuttlebug or other similar machine. I like this new folder I got from Sizzix.
Color the raised areas with oil pastels.
Paint over the entire surface with gesso and let dry. I'm not sure if it's the brand of oil pastels I used, or that I used a thick application of the oil pastels, but the gesso turned light green when I painted over the pastels.
Sand the raised areas as much or as little as you desire to reveal the oil pastels colors underneath.