I used a thick poster board, crayons, and a hair dryer. It took a bit before the crayons actually started to melt down the board, but part of the problem was that I had the hair dryer on medium instead of high (didn’t realize it for like 5 or 10 minutes. Once I turned it on high it went much faster).
The poster board wasn’t the best medium to melt crayons on but for my first time ever, I’m thrilled! LOVE the bright colors. I bought some canvas this past weekend so I will try again another time with that. Really excited!