Check if the whale’s tail is firm. If it is, start making the tail fin. Add some CMC to 5 g of mint blue paste (you want the paste to be slightly thicker so that it will hold the shape quite well, but you still need to be able to shape the fin without the paste cracking – see next steps).

Roll out the paste so that one side is about 2-3 mm thick and the other side about 1 mm thick (gradual change of thickness). Cut out a circle (I used a 4 cm cutter). Make two cuts with a wheel tool as shown in the photo (base of the fin - thicker; ends of the fin - thinner).