I have pieced 4 large quilts in sections and am currently working on my 5th. I love the technique! I watched Marti Michell at Puyallup's Sewing and Stitchery Expo a year ago, and then bought her book: Machine Quilting in Sections. I've used two or three of her techniques and find myself going back to this book again and again.
When I'm sewing the back by hand, I do it at my ironing board. I position the quilt so that the seam to be sewn runs toward me on the board, so the quilt is being supported on either side. I find that it's much easier on my hands not to support the weight of the quilt that way and everything stays stable since the weight of the quilt is not working against that seam being straight. It doesn't take long at all to finish up the quilt. I do have one of the slightly larger ironing boards (bought at Costco).