I have NEVER gotten down on the floor to baste a quilt! I use a 7 foot table (that's only 84" long) to baste any size quilt.
I use large bulldog clamps from the office supply store to stabilize the layers, one at a time, leaving excess length hanging off each end.
Starting in the middle I hand baste, without boards although I've tried them and they're okay, going from the middle to one side as far as I can go. I leave a long length of thread at the start so that I can rethread the basting needle and go the opposite direction when I 'm ready to.
Then I leave the thread and needle in the fabric, start another row of basting about 4-5 inches apart, and baste in the same direction, and stop as I did before.
After I've basted as many rows as I can on that width of the table, I rethread the needle and baste the other direction as many rows as possible.
At that point I unclamp the layers, shift the quilt one direction or the other, adjust and reclamp the layers, and continue the basting of the previous rows to the edge of the quilt.
When that is done I unclamp, shift, reclamp, and baste as needed to finish the quilt.
This process takes me the better part of an afternoon, or even a day, but it's my preferred way above all others.
Quilts that I have basted have been dragged around, hooped and re-hooped, folded, opened, spread on a table, refolded, turned and rehooped yet again.....and I've NEVER had a problem with the layers shifting or coming apart. And when I handquilt, it takes a year or more!`
Jan in VA