You have several choices for how to make the board. Each square should be 4x4. I recommend getting one of the 10"x10" base plates, which have Lego dimensions of 64x64, and then adding plates for the colouring. Alternatively, you could do what I did which is to make the board out of whatever Lego plates I had available, making sure that the top was of the correct colouring.
Here's the base plate I recommend: 
Here are some shots of the board and pieces:
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