I have never used foamcore board so please excuse my ignorance...LOL...

Can the cake sit on the foamcore board....
How do I use this to stack a wedding cake?

For a wedding cake, I would double the foamcore (for added stability) and it must be covered in something, usually cake foil, before placing the cake on it.

You need to have some kind of barrier between the cake and the board. Look at some cake drums as those are sold with a silver or gold aluminum foil looking cover in place. You can recover it or use it as is, as long as it is food safe (card board cake rounds will do just fine as a barrier). They are pretty heavy duty for stacking, tho. I glue a couple of card board cake rounds together for the cake to sit on when stacking. There are some ideas in here. http://cakecentral.com/cake-decorating-ftopict-654103.html

so I can cut and use 2 of the foamcore boards wrap them in foam and use this for added stability?
OR
use a cardboard cake circle and the foamcore board wrapped in foil?

sorry meant to say foil not foam

I know at least one of those links had covered this discussion. Try Wilton.com for how to stack a cake.
* sorry, woke up with a headache. Go to the Wilton site and find the lesson on how to stack a cake. They use foil covered foamcore and cardboard circles and show how to support your tiers. Everyone needs to watch it at least once in their career.

I love this video:

Oh...and almost forgot this one: