It looks like it has the wedges where the flowers are at with one main center dowel for supporting the layers. I'm not 100% sure since I've never done anything like this. But to me thats how it looks.
im not an expert on this, and have never done a cake like that, but i think the way i would do it would be:
get some styrofoam the size of the cake plates and make sure you have a pocket level handy. put your wedges where they will be center on the top of your bottom cake layer. find the level middle and carve away the styrofoam till it is the angle you want and stick your next layer to it with your cake plates and pegs and such. then put another wedge on and find your level middle of it. (it should be angled to the bottom of the wedge but level with the table) when you find level middle carve the top of the block until it is angled in the opposite direction of the first wedge. then put cake layer 2 on this one with the cake plate and pegs and stuff. continue the process until its done. you also might want to mark level middle on your wedge with a pen or marker to remember where it is. the wedge will be covered anyway. hope you could understand that and that it helps you some.
This link should tell you alot!
You should pm ShirleyW on this one!