If I want to quilt a dummy cake, do I need a layer of icing underneath or will it work fine just with the thin coating of shortening like I usually do?
I use nothing under my cake dummy but doing it your regular way would be fine.
I mean...will it make a nice quilted diamond look if there's no icing underneath?
It should... but maybe you could roll the fondant a bit thicker if you don't get the look you want.
Yes it would Kitagirl.