Part II Forgot to add 4 1/4 x 2 1/2" with 1/4 20 threads bolts and wing nuts the bolt head depends on what you want to tighten the bolt with a screwdriver or a wrench.
Take the long boards and place them together flat on the 2" side using a square mark a line one foot from both ends and 1/2" up from the bottom of the boards drill out a hole using a 1/4" drill bit.
Make 3 frames out of the 1 X 2s putting the long boards inside the short ones and square them with a square.
Put some wood glue on the frame and nail down the hardboard with the textured side down if you set the nails you can fill the holes with wood filler or wall board filler.
There is the table portion of the table now there are options for decorating it.
I personally would not put any thing on the table it self I would put it on inso foam so you can have ether a city fight table or a grass field table.
So for the city fight table get some 1/2" blue or pink inso foam cut it down to three 2' x 4' sections like the panels before using drywall filler fill the brake slits in the panels and paint with house paint color isn't mandatory but dark Grey will let you skip a step with a lighter color Grey dry brush the panels to give it a cement look.
So for the grass top I would do the same up to the color of the paint but use green paint.
Then I would get some stuff from Woodland Scenics
http://woodlandscenics.woodlandscenics.com/show/category/GroundCover/
Pick your color and type of grass and I also recommend there cement and fixative stuff as well.http://woodlandscenics.woodlandscenics.com/show/category/ToolsAdhesives
The trees they have are cheaper than
GW but I recommend spraying them with the fixative as well.http://woodlandscenics.woodlandscenics.com/show/category/Trees
You will have left over hardboard and foam you can use this to make small hills and woods for the grass field table cutting shapes out of the hardboard then sanding the edges to smooth them over and then cutting the foam slightly smaller than the hardboard and cutting a slope on the hill for miniatures to stand on.
sawhorse's are a cheap way to make legs with the panels bolted together a sturdy way as well I would also recommend some squeeze clamps to hold the table to the sawhorse's to prevent the catastrophe of someone bumping it off them.