I saw a picture of this on pintrest but I have no idea who first posted the idea.
The canvas I used is about 24x30cm with a 24 pack of crayons. I had no idea where to put the brown and pink so they just got end spots.
Hot glue the crayons to the canvas in whatever order you like.
Set up somewhere you don't mind getting a bit dirty (wax might fly).
I used the high setting on my hair dryer so it melted faster but it made the wax move around a bit. If you want straighter lines use a lower setting and use more time.