This was done on buttercream, which is what 99% of my clients ask for. Ice the cake and smooth it out, then cut some strips of fondant about 1/4"-1/2" wide. It doesn't need to be precise.
Coil up one of the strips and insert it into the cake where you want the center of the pattern to be. If you want to do something totally symmetrical just coil the stip around the center, pressing the edge of the strip into the icing as you go. If you want to be more freeform, just wind the strip around cornelli lace-style.
When you've covered the entire tier, go back and fill in any spots that look like they could use an extra piece. You want the pieces to be relatively close together to mimic the fabric strips that are sewn on to make the floral patterns.
Press the pieces into the icing with a fondant smoother to make sure that everything is in place and secure. You are now done.
Kara Buntin owns A Cake To Remember LLC in Richmond VA, and cake supplies online at www.acaketoremember.com and www.acaketoremember.etsy.com