When I put the backing on my table for layering - I do put a "light tension" on it - just enough to keep it from bunching up when I add the batting and top .
What I do - I do smooth it out - and tape the ends to the table with masking tape - and the part that hangs over - I make a temporary "pocket" and put a yardstick or curtain rod into the pocket to keep it from wrinkling on me.