Trim a 16 in. Featherweight decorating bag to fit tip 789. Fill bag half full. Starting in center of cake top, hold bag at a 45° angle, lightly pressing the serrated edge of tip against cake. Squeeze a ribbon of icing in a continuous spiral motion to cover cake top, with last ribbon forcing icing over the edge of cake top.
To ice the sides, squeeze icing as you turn the cake slowly on the Trim 'N Turn turntable. Repeat the process until the entire cake side is covered.
Smooth the sides of the cake by leveling the icing with the edge of the Large Angled Spatula. For easier smoothing, it may help to dip the spatula into hot water, wipe dry and glide it across the entire surface. Smooth the top using the end of the spatula. Sweep the edge of the spatula from the rim of the cake to its center. Then lift it off and remove excess icing. Rotate the cake slightly and repeat the procedure, starting from a new point on the rim until you have smoothed the entire top surface.