Not sure.  You could put something inside licorice whips or thread them onto dowels. If not being eaten, you could use stiff wire and take it off before folks eat.  If cake was flat can just pipe rope pattern.  Makes it trickier if you don't have fondant/gumpaste.  Or maybe bake something in an arch with a cookie or biscuit dough and pipe over it but not sure it would work or hold up for long........  My Easter cake in pics was flat and piped with basket weave.