Well, my way is different, I sandwich my quits standing up...something you might want to think about. I bought 2 sheets of rigid insulation that is 4'x8'...cut one of them in half length wise and duct taped them together so I have a design wall that is 6' wide and 8' tall. I did not attach it to the wall because I move it around in my house, and also take it outside to use. I use spray baste from Hancock's to sandwich my quilts.
1st step: pin the backing all away around to the design wall by smoothing from top to bottom and side to side having the wrong side facing you and spray according to directions.
2nd step: pin batting along the top of the backing leaving the sides and bottom unpinned, spray batting on the side that will be stuck to the backing. Start smoothing at the top of the batting and work you way down (I start in the middle of the quilt and smooth to the outside, like hanging wallpaper).
3rd step: pin top to the batting and backing along the top only with the right side out. Spray batting and back side of the top and then smooth all the way down, starting in the middle and working your way down.
4th step: optional - I use a few safety pins, about 1 every 2 feet, just to stabilize the quilt until I am ready to FMQ and bind.
I am 73 years old and this is the only way I sandwich a quilt. I do have to climb up on a step stool because I am only 5' tall, but that is much easier than crawling around on the floor! I move everything to the garage if the weather is bad so that I can't open doors and windows. Also, I don't have any problem with overspray because I stop about a foot from each edge. If a little gets on the floor it doesn't seem to be a problem.