First, we put our wood pieces on a cookie sheet in a 350 degree F oven to heat up. Once the blocks were hot, we set them on the towel-protected table and we each drew on ours with crayons. The crayon melted as we drew, just as it did with the melted crayon rocks, although not quite as dramatically just because the wood didn't get as hot as the rocks did.
While I didn't feel that working with the hot rocks was safe for my two year old, she safely drew on the hot wooden block and wood pieces alongside Maia and me. The wood didn't hold the heat like the rocks did and the risk of burning was much lower.