My 4yo had so much fun making some lego crayons out of his old broken crayons using a sicilone ice cube tray. You could make any shape you like depending on what ice cube trays you have available.
To do this, simply take the wax crayons you want to use and make sure all the paper is removed. Break them into small pieces and overfill each compartment of the mould. Place the mould onto a baking tray and then place in the oven at 160degC for about 8-10 minutes, but keep a watch and check after 5 minutes – remove as soon as the wax has melted. Leave to cool on the side and once completely cooled, remove from the mould. You’re left with a colourful army of lego men!
Here is a link to the ice cube tray. Please note that this is an affiliate link, which means that if you purchase the tray here I get a small commission at no cost to you.