My most popular and asked for cake is the WASC. I make it with the smaller box mixes and have no problem. I have tried adding the 1/3 extra cup of cake mix and see no difference so gave up going to the extra trouble.
My best guess would be a five petal cutter, slightly ruffled on the edges, bunched together in the center and attached. I just did a similar cake by cutting 1 1/2 inch circles and folding them for a ruffled effect but has a little different look than this.
What Leah_s said! Order SPS immediately! Viva paper towels work great on a crusting buttercream. I use indydeb's recipe found on here from time to time. Will smooth perfectly. Round is much easier to decorate than square. Good luck!