The completed cake

Here is the promised picture of the celebration cake with its cardcraft topper. I was very disappointed when I first applied it because it didn't sit flat and I couldn't understand why - I'd turned the cake upside down to give a good level surface for the marzipan to be rolled on, and then the fondant icing was also rolled over the top. So how did I manage to have a point in the middle, on which the topper wobbled like a pea on a drum? More importantly, what could I do about it? Double sided sticky tape didn't seem to be the right answer, and pins round the edge wouldn't be much better.....fortunately when I tried it again a little later all was well and I decided it was the card circle which was out of true because of the uneven thicknesses (three layers in the middle to one on the edge) so I put it inside a large heavy book overnight and I think all will be well.