1. The most important technique is as soon the icing is on the cake, secure the corners immediately.
2. Use both your hands and work on the corners first. Push the icing right down the corners and manipulate the icing on the straight side to achieve a neat finish.
3. Once the icing is trimmed all around the base, use the acrylic smoothers as for the round cake.
4. For a sharp edge use two flexi scrapers and work them against each other to achieve a sharp edge.