I realize this is an older post, but those I'd throw in my .02 worth.
If the belt is just off, what I've done is just lower the deck (not dismantle.. just use the lever to lower it) depress the clutch with my left hand and use my right hand to follow the belt and place it back on the back pulley.
If the belt is just off, what I've done is just lower the deck (not dismantle.. just use the lever to lower it) depress the clutch with my left hand and use my right hand to follow the belt and place it back on the back pulley.