Make sure your moulds are wrapped up well with towels and/or rugs, after you've put the soap mix in them ... the soap needs a few hours to gel and during that time it gets quite warm (this is the lye working on the oils and making soap ... so make sure the moulds ar on something that won't be damaged by heat. I use a oven rack and have the towels going under the rack, up and over the moulds and tuck in the sides to prevent any draughts. Be careful not to move the moulds, so that the mix moves and sets unbalanced.
Cover the moulds with cling wrap ... before wrapping towels around them. This helps keep the heat in.