We peeled the paper off of all of our crayons and glued them onto the top of the canvas (we went with a rainbow pattern, but you can always pick your favorite colors and make it your own). We made a thin piece of duct tape and wrapped it around the glued crayons to make sure they wouldn't slide off the canvas if the glue got too hot too.
We sat the canvas in the sun around 1 p.m. and let the sun do it's work. We checked in a few times to make sure the shadows weren't covering the canvas. Make sure you're picking a very open area to place your canvas for prime melting experience.