Its was overcast and the lighting was dim, but I clicked this pic to show some fondant feeding on top of a five frame nuc. The nuc has a two inch or so spacer placed on top to allow room for the fondant. The fondant was placed, and the picture taken about 20 minutes later.
Last year I fed some nucs this way with varying success. I could place up to 20-25 pounds of fondant this way and it was enough for at least a couple months feeding.