To float the batting, all you do is anchor it down to the backing (I do this with my LA - just baste a straight line across the top of the backing and batting). And then simply push it under the 'top' or 'belly' bar, and over the backing bar - letting it hang down. Then of course, your quilt top would go on next. You can float it the same way (save your basting for both until here if doing it this way) and let it hang down (pushing it beneath the belly bar and over the backing bar).
I almost always float mine - just faster and I have no problems. I figured out the fastest method for me, after trying every single I read/learned about. I learned to baste with the LA so there are no pins on the velcro leaders. I can rip them off and on and change quilts or test pieces in a second, once the quilt is basted to them. Easy peasy :)
I show the basting on a utube video I made. Search for 'DebbieHQ'. It's in 3-4 very small videos as I didn't know how to combine them (silly me!).
Debbie in Austin