Sort of a deviation on a same theme : cast the pich on a flat surface (very even thickness achieved easily), then use stick (or better, double stick, with a spacer) to quickly mark the surface in a warm pitch (it will look like a chocolate block after that !). Then put it into a freezer to cool down; it will easily break down into squares when cold. Then glue the squares like explained in Texerau, using a Bunsen flame or a candle.
Bratislav