I recently got these cold lego molds from Amazon and thought they would be perfect to use:
1. Preheat oven to 250 degrees.
2. Remove all the paper from the crayons. If you take a razor blade and cut one line straight down each one, it's very easy for kids (and adults) to remove the paper. I usually cut the paper and let my kids remove the paper.
3. Cut or break the crayons into smaller pieces. I usually use a knife. Be careful because they'll go flying when you chop them up sometimes.
4. Place molds on cookie sheet (pizza pan works great) and place in oven for about 10 minutes (or until the crayons have melted completely and you do not see any lumps).
5. When done, carefully remove from oven. Careful not to shake too much when pulling it out or the wax will spill. Allow molds to cool completely. Uusally after the pan has cooled, I set the whole thing in my freezer for about 10 minutes. It seems like this helps to remove them from the molds and prevent breaks. (It's important to fill the molds as thick as possible - thinner ones break easily when removing from molds)
6. You're all done!