I had a lot of trouble just like you until I bought a large fold down table at Joanns. I have trouble getting up off the floor once Im down so could not do it that way.
I use those big black paper clips that you fold shut to hold the backing tight to the edge of the table. It works every time.
The table goes on sale for $50 so watch for it or use a 50% off coupon.
It is well worth the investment.
I have used the spray and the iron on batting but this works much better.
I also use cotton batting now. I use the bent safety pins that are easy to use and the quick pin device that you can buy at Quilt In A Day web site.