I like to match my cake boards to the cake design. I use wrapping papers, fabrics, and foils.
I start with 1/2" foam core.
If I am using a paper, I just cut it a little larger than the board, and make little slits along the edge so I can fold the paper down over the board and tape it to the bottom.
If I am using fabric, I first spray the board with some spray adhesive, and then smoothe out the fabric. I then fold the fabric over the edge of the board and tape it to the bottom. I do this several days ahead of time to make sure it dries and the fumes go away before I cover it with contact paper.)
I cover both the fabric and paper covered boards with a layer of contact paper to make it grease-proof. I also do this several days before the cake will be placed on it.
**Note: I ALWAYS set the cake on a plain cardboard cake circle that I then attach to the covered cake board with double sided tape. My cakes do not touch the contact paper.
I finish it up with a coordinating ribbon.
Here are some examples:
Hope this helps.