I am no pro but I imagine you can use a pillar set and just fill in with the carnations.
I'm no expert--not by any means, but I would do the cake layers on double or even triple layer cakeboards above the styrofoam layer with the carnations and put dowels through all 3 layers.
I remember you talking about this cake awhile ago on another forum. I can't wait to see your finished product! I'm a big fan!
It kinda looks like the pillars cause it seems like the edge of the plate is sticking out of the cake a little. That would probably be the safest and sturdiest I would think. I'm no pro either though.
I'm making the same cake in October!
I'll be using the sps and alternating 12" and 10" cakes, the 10"cakes will be studded with carnations to get the flush look - if they were all 12"s they would sitck out and the bride wants them flush-ish.
The wilton hidden pillars or push in pillars ... then just fill in the space with the flowers.