pipe a bead of frosting onto the back of the flower? are they being put on the sides or the top?
Attaching royal icing flowers can be done by either piping a circle of BC frosting on bottoms of dried flowers if they are smaller, then attach to cake, be it sides, top or bottom. For larger side flower, pipe a royal icing spike to bottom of dried flower. Let spike dry for 24 hr period or at least 12 hrs. Then attach to cake by adding a little BC frosting to bottom base of flower. Also, check out Wilton website, they use to show how to take floral wire, bend a tiny loop at the end, dip the wire in a mound of RI on wax paper squares, hook the other end of wire on rack to let the RI end dry 24 hr period, pull off wax paper square, then attach flower with RI. Tooth picks and skewers work the same. HTH
If your flowers are on wires, get the wilton lollipop sticks, they are hollow in the center and you slide the wire through it then stick it in the cake. the lollipop stick will keep the wire from cutting through the cake. I have also seen where people have used cofee stirrers, slid the wire in then filled with royal icing.
I use buttercream to attach them with no problems.