Thanks in advance! 
are you or your client delivering it? if it's you i'd assemble the flower on site but either way -- i'd attach the outermost petals into the side of the cake and use melted chocolate as needed for glue especially for the center -- which could be made with a spike in the back to also insert into the cake --
looks like nice crispy fondant -- could be gum paste -- but i would make it with crispy dried fondant so the candy can be enjoyed
Looks like white chocolate to me. I've done a few using it.
http://thecakeblog.com/2017/05/white-chocolate-flower-cake.html
It's pretty fun and pretty easy to do.
it does look exactly like that --
who is delivering it?
My first thought is chocolate as they aren't all uniform and have that groove down the center of each petal. Chocolate it so fun to work with!
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