Am currently hatching a plot for dd's 3rd birthday cake, and am going to have a go at Annabel Karmel's parcel cake. I'm planning to use pre-coloured ready-to-roll icing on an 8" square cake but am worried I'll end up with messy corners on the base layer. All the tips I've seen elsewhere on using this type of icing feature round cakes, which I think might be slightly easier. Any clues as to how I can get smooth corners? Thanks!