To make fondant stick to a cake or other baked good, spread a layer of any sticky substance on the cake. Buttercream frosting and other types of frosting are possible substances to use. Only a thin layer is needed to help the fondant stick. Make sure the layer is evenly spread around the entire cake, including the sides.
If you are attaching fondant to other pieces of fondant, such as for cake decorations, water is all you need. Use a brush that is dampened, and brush it on both pieces of fondant that need to stick together. Use only a small amount so it doesn’t slide around too much. If it slides and the fondant is colored, a tinted residue remains. After you apply the water to both pieces, press the top piece of fondant to the bottom piece, pressing lightly and smoothing as needed.
For fondant that is going on a cake, make sure the rolled fondant is prepared before you ice the cake. This keeps the frosting from drying too much before you apply the fondant. Begin by rolling it until it is approximately ¼-inch thick. Let it dry for up to 36 hours. Let the cake cool, cover it in buttercream or royal icing, then place the fondant carefully over the top of the cake, smoothing it over the top and sides.