I don't know if what I do will help or not, but I put mine together on my dining room table. I have to move it three times to get the whole top pinned. I do the center first and then each side.
I tape the back down with masking tape, and I bought some big clamps from Harbor Freight to hold the bating and top down. I also use lots of pins.
You will find a way that works for you. I'm fairly new, but I figured out quickly that doing it on the floor just wasn't the way I wanted to do it.