I made this top quite awhile ago (it was a Jelly Roll Race, but I didn't use a jelly roll). It sat, waiting for me to quilt it. Finally, I had the perfect opportunity- I took a class on basting at Pine Needles, and needed a quilt top. Thank goodness for procrastination- I had one!
The basting class was all about how to use a table top corner to pull your backing flat to your batting and then how to layer the top on it. You let gravity do the work. I still think it would be tough for a king size quilt, but certainly easier than crawling around on the floor. I was about as effective at no wrinkles in the backing as normal (meaning there are one or two tiny puckers).