Was thinking about just one large wasteboard for now. Will just use double-sided tape. What would be the perfect size for me to get Home Depot to cut me a piece out of some MDF?
32.25" x 32.25" is the largest cut area you can achieve so that would be my recommendation for a WB size.
If you factor in the cutting diameter of the surfacing bit (mine is 1-1/4"), you can go a little larger. My wasteboard is 33x33 with t-tracks along the y-axis border.