Cut the dough in half and put one piece back in the freezer. Roll the remaining half out to a 3mm (⅛in) thickness on a polenta-dusted work surface. Cut the biscuits into 5cm (2in) rounds or squares, using a circular cutter, drinking glass or pizza wheel. Repeat with the other half. Transfer the biscuits to the prepared baking-trays. Use a fork to prick the top of each one once to prevent too much expansion during cooking. Bake for about 15 minutes until golden. Rotate the trays halfway through cooking to avoid uneven browning.