The last tardis I made, I made the sides weeks before (1/2 and 1/2 flower paste and sugarpaste) and dried them then just attached them to the cake with butter cream. I made the top separately on a board so I could cover it as one piece then stood it on the cake before I put the dry sides on. I followed this roughly and without the electrics! I also sent it off for DH to deliver and he forgot to take pictures! I may have cried and yelled a little!