I am making a Stanley Cup out of 5x8", 3x6", 3x4" half rounds plus a half bowl for the cup.  It will be half of the Stanley Cup lying flat on the board.  The flat side of the half rounds will be on the board. (Sort of a 2D orientation, but with shape coming out of the board)  What do you suggest to keep the layers from wanting to separate?  Do I need to worry if half an 8" is my largest diameter?  I'm using straight buttercream.

Thanks in advance, folks!

 Never have done it but from what I read on here I suggest you crumb coat with ganash   It will set up hard & hold things together — act like a flavorful glue:)    Also if you use a blob of b’cream on the board & as a filling between the layers that should also help 

yeah what lynne said, buttercream alone will also do well 

I cannot get a visual on this???  No help from me.