I have one of the cutting tables like are sold at JAF with the sides that fold down. Mind you, the sides are never down, lol. I pin from baby up to king size quilts on this table. I use the big binder clips that you can get at the office supply store. I start in the center of the quilt laying out the backing and clamping that in place. Follow with batting and clamp it and then the top and clamp that. I pin about a hand-width apart in each direction. Unclamp and slide the whole quilt sandwich every which way until I'm able to clamp and pin the entire quilt.
It's tedious and tiring to do a king size quilt this way but it sure as heck beats crawling around on the floor!