Gingerbread Exchange Community

Fondant will stick, as long as you apply it with some wet royal!

Depending on how smooth your royal icing patch work is you may need to apply a thin and malleable layer of fondant which you can smooth out with your fingers and then place another layer over the top that will give you the proper smooth finish you want on walls/roof pieces.

I stick fondant pieces together on cakes with royal icing, and it is wonderfully good at sticking when it hardens.

If this is still giving you problems you might try a technique a British friend (professional cake decorator) uses for an ultra smooth surface.  Between either the cake (as she does) or the RKT, put a layer of marzapan (almond paste) rolled out like the fondant is.  She has made our daughters wedding cakes and they are always perfectly smooth, without a lump or bump.  She also uses apricot preserves, thinned a bit with water, brushed on the marzapan, to help 'glue' the fondant to the cake. Generally Americans don't like the flavor of fondant, but she makes her own!  The marzapan is just one more delicious layer!  You can buy it ready made on Amazon, by the way.