The setup I use for handling extra-large game boards (like the one for The War Game: World War II) is to place several card tables (the kind with legs that fold for storage) end-to-end.
I find that card tables work well because they’re inexpensive to buy, they give you the option of getting as many or as few as you need, and they’re usable regardless of whether or not you have space to devote to a full-time gaming area. If you’re short on space, you can set them up temporarily for a game then fold them and put them away when you’re done. If on the other hand you have enough room to leave them set up long-term, the space under the row of folding tables can conveniently serve double-duty as storage space for your game equipment. That’s where I keep the plastic tackle boxes in which I store my A&A sculpts.
Depending on how smooth the combined surface of the table-tops is, you might want to put something stiff in between the tables and the game board to provide a more level surface (which can be helpful when the game board is in several pieces). Foamcore posterboard is one option; another is a material called (I think) coroplast – basically it’s structured like heavy cardboard, but it’s made out of plastic. I buy mine at a store that sells artists’ supplies.
CWO Marc