My studio floor is black and white 12" tiles, and after a careful sweep I am confident about laying the top on the floor and taping it down for the big squaring off. I have pictured the Quilter's Rule and my hand sliver of soap marking tool. Both totally necessary items for this process.
Once all four edges are marked for the squaring off, I gently place the top on the flattened batting. I haven't cut it square on the floor, as my knees can only stand kneeling so long. I can cut it on the table more easily and can just tug at the batting to aline the next area to be cut. At this point it is only placed on the batting, and after it is trimmed, I will then cover it with a press sheet and steam and press with a hot hot iron until I feel the thing is entirely fused to the batting .