You are right, I just put it together this weekend. The overall size is 18"x24" and I found that a 5 x 5 grid worked nicely and left some space on the sides (approximately 2 3/8"). I'm a graphic designer by trade, so I just did a little measuring to get the top and bottom corner cards in the right spots, used a straightedge to get the top row in place, and then eyeballed the rest. I used "Scotch Photo Splits" which are these tiny adhesive squares, I think used by people that scrapbook, to stick the cards to the board. They seem strong enough to hold it, but can peel off without major damage to the cards.
Wasn't too hard to put together and turned out nicely I think. Could probably put another one together for $20-25 or so, with just a little time for cutting the matte board and doing some measuring. I just need more decks now, so that I can get 25 extra cards worthy of displaying.
Here's a few other pics, detail views of this little thing, should anyone be interested...
http://cl.ly/BaCFhttp://cl.ly/BaWNhttp://cl.ly/Bbcs