Tabletop Gaming Boards don't come much better or bigger now that the Citadel battle ground has been given extensions that can make it 8 ft x 4 ft !I found the Realm of Battle gaming board a touch on the expensive side but it's such good quality that it's difficult to imagine being able to produce a better homemade diy board.
One thing that GW's gaming table does really well is the hills. Your troops can actually move up and down them without falling over ! Most homemade boards have stepped hills or (worse) hills that are smooth but too steep and not navigable for anything other than a metal behemoth on a monster base.
These extensions mean you have a few more customisation options and the board is better sized for 3000+ pt battles (or even 2000pt battles if you're deploying "horde" armies)
More details on the GW website - Realm of Battle Board extensions
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