I'm making a queen size log cabin at the moment, and am doing it in quarters. Quilting to within an inch or two of the edge on each piece, and then stitching the top together, trimming the batting to butt up against the adjoining piece, and then I'll hand sew the backing closed (leaving a bit of overlap). Then, I'll just quilt those final joins at the end. Well, that's the plan at least. ;)
If your top is already together, maybe try one of those spray-on adhesive-basting products? I don't know. I'm sure you'll get better suggestions from the other folks here!
Good luck!!