I have a bride who would like a 3 tiered stacked square wedding cake. I only have circle masonite ones that i got from a place that is now no longer in business. The cake is for October 13th. I been hearing about 1/2" foam core boards. Is it easier to make your own or purchase pre-made ones? I have searched and found one source, but they seem expensive for a 16 or 18" ones.

Any suggestions is greatly appreciated.
Thanks!

If you're asking about the base board instead of internal support boards, I'd use plywood.
(or search for drums.)

My local lumber store cute plywood for me. It's very inexpensive.

Sometimes I cover it with foamboard if I am covering it with light fondant