We recommend fire-safe containers, but you can get creative with other options too—just make sure they're spacious enough. The key is to keep the melt pool away from the edges and ensure your vessel stays cool while burning. Aim for at least 10 cm in width at the narrowest point, but always test it out to make sure it stays chill when lit.
For the best burn, keep at least 5 cm of sand wax around each wick (one wick per 10 cm wide container!) and leave at least 2.5 cm between the bottom of the wick and the base of your vessel.