Make A Sugarpaste Bicycle How Do You Ice A Cake With Sugarpaste To Make It Look Like A Box With A Lid On?

How do you ice a cake with sugarpaste to make it look like a box with a lid on? - make a sugarpaste bicycle

The only way I can think to do is to cover the cake and then cover a layer of ice to put on. This doubles the thickness of the ice (not) very nice. any help would be very grateful.