easy….thread line through bait band
tie an overhand loop then you should have a free moving bait band incorporated into the loop. then carry on tieing the rig as usual

pull hair loop through bait band then thread hooklength and hook through loop and pull tight. Or fold bait band over loop and then pull the band through itself and insert pellet into band

all i do is the tail left from tieing the hook i thread through the band twist about 5 times and the first gap by the band i thread the line through and pull tight you can also slightly adjust the lenth before pulling tight

See how I attach it on this article, (see pellet waggler rig picture).

http://www.fishing-world.co.uk/matchtips/fishing-the-dumpy-waggler.html

Another way is to thread the line through the band. Then tie an overhand loop so it becomes the whole length of the hair. Thread the other end of the line through the eye and pull the little overhand loop knot right down tight to the eye. Now wrap the hair loop around the shank just once, then when you tie the knot lessknot, the tension will then unwrap it, straightening the hair back, ensuring it hangs straight from the shank.
Can I ask, why do you want the band free running in the loop?