You could take four or five turns of the rope around the stick to lock the rope (overlap the initial turns with subsequent turns to keep them from slipping), then hold the stick with the rope between your ring and middle fingers and use the pinky finger to help grip the stick. That leaves your thumb and index finger on the same hand to assist in tying the clove hitch. Once the hitch is in place and dressed, roll the stick slowly to release the lock and you're left with just the clove hitch (at a cost of only a few inches of hanging height).
Also, when the bag is heavy, using a rope-locking stick makes hoisting easier and the rope is less likely to slip through your hands. You can lock the rope around the stick while the rope is under tension: hold the stick almost parallel to the rope, rotate the stick around the rope so as to gather a few turns, then rotate the stick perpendicular to the rope. Usually, the turns will slide together and lock.
(I hope this isn't excessive detail, but I figured if I was going to write it I might as well be complete.)