This probably isn't as good as some of the other ideas here, but when I have pinned a quilt on my floor, I put the pins in but didn't close them while it was on the floor, then I sat in a chair with the quilt in my lap to close the pins. Reduces floor time!
You might also consider using white glue to baste instead of pinning. I think you could apply the glue while standing, except maybe near the edges where more precise aim would be needed. I haven't done glue basting a lot, but maybe someone who has can comment further.