I used a box when using the hair dryer to melt the crayons.
It took awhile for the wax to melt, but once it started, it ran quickly. Eventually they were all melted and it all ran to the bottom of the box - it actually leaked through the cracks in the box. Thankfully I was on a slate tile floor so as soon as the hot wax hit the cool flooring, it became firm immediately! I was so relieved that I didn't have a huge mess on my hands!
The Finished Product
Now I just need to figure out where I want to hang it! :)