I am making my first wedding cake this weekend and the bride wants a fondant ribbon around the middle of each tier. The cake will be iced in buttercream. How do I get the fondant ribbon to stick and not slide down the cake?
Use buttercream as "glue" for the ribbon.
It is easier if your butter cream is a crusting variety and if you do, then lightly moisten the area where the ribbon will be attached before adhering (I just use gum glue) or better yet measure and use a ruler and mark your placement and then pipe on a line of icing exactly in the middle of where the fondant ribbon is to be adhered. Also, if the fondant ribbon width is very thin you might need an additional set of hands to get it into place as the middle of the roll tends to slip out if the length of the ribbon is long because the tier is very large.
Roll the fondant out thin ( less than 1/8" looks best). Sprinkle the fondant ribbon with powdered sugar (so it won't stick to itself in the roll) and then roll it up. Start in the back of the tier and adhere the end of the ribbon and then unroll and turn the cake making sure to keep the ribbon exactly in the middle. When done, use a brush to remove the excess powdered sugar. HTH