I had my brother build my cutting table (he's my 'cabinet guy'...). It is 38 inches high which is about two inches higher than the ones you buy at JoAnn's or wherever. I have lower back issues, and the extra two inches in height seems to help. In fact, my brother built all the cabinets in our house and all the countertops - kitchen, bath, laundry - are 38 inches high (standard ones are 36"). Makes a huge difference in terms of back pain caused by bending over.
The top of my table is big enough to hold two 24x36 cutting mats taped together, with a couple of inches extra top and bottom, and about 6 inches extra side to side. That way I have room for rulers, pin cushions, rotary cutter, etc., off to the side of the cutting mat.