I just went through the process recently and the way i did it was very simple. I went down to the Home Depot and bought an 8' by 4'
MDF board and had the guy cut it into four 2' by 4' boards. I also bought a pair of eight foot 2" by 4" planks. Then I bought two adjustable saw-horses. I thne painted one side of all the boards green for country fighting and one side grey for cityfights. I put the two by fours across the saw-horses and then laid down the table segments for an adjustable, modular board. You can see the results here...
zombievisions.blogspot.com/ I imagine to get a bigger table all you would need to do is get more
MDF segments and a few 6 foot 2" by 4", and then lay those across the other boards. Although that might be less steady, so it might be better to just add another pair of saw horses. Nothing would be worse than having an apocalyptic miniature accident. But you could probably get all the materials for around 100 dollars or so and my table is very steady.