That lid is actually a cake board. You can build up the height of the lid by using a torted layer of cake (or cheat with rice krispies + marshmallows). Place dowels in the lower cake--they will have to be different heights to get the tilt, shorter on the inner side, taller on the outer. Test it out with the undecorated lid, making sure the angle isn't too severe--wouldn't want to risk slipping. Decorate the lid, then position on dowels. Hide the dowels by using gumpaste (or gumpaste/fondant mixed) decorations, such as tissue, flowers, etc.