Doing so will ensure symmetrical buttercream flowers every single time, so you won't have to worry about disproportionate or ...

Cut the cake in half horizontally. Add a generous layer of buttercream to the bottom layer of cake and then place the other layer on top. Transfer the cake to a serving board or cake stand.

For the dark chocolate buttercream, repeat the method ... then top with the 15cm/6in cake. Decorate with fresh flowers.