Help! Does anyone know where I can get good cheap, full size sheet cake boxes?- That will fit 18" x 24" cakes.
Do you have a warehouse store like Sam's club, BJ's or Cosco near you? They will sometimes sell you their cake supplies. Otherwise www.cakedeco.com has full sets (tops, bottoms & cake board all together), but you have to buy 20 sets. If you itemize the price, it's about $4.59 per set. I have them and the boards are nice and sturdy and fit perfectly. HTH.
You can also use 2 12"x18" boxes together to MAKE a full sheet box. 1/2 sheet boxes are a lot more 'available' in cake supply shops.
Unless you absolutely have to have a box, I'd just cover the cake w/lots of plastic wrap.