I pre-tie my leaders, too: barrel swivel / line (4-6 ft) / hook.
I then stuff them in individual ziplock sandwich bags, but there is a trick to this. Put the hook end in the baggie first, then push the line into the baggie - a foot at a time,
but leave the barrel swivel end hanging out, zip the bag shut, label the bag with line weight & hook size.
It will not be tangled. Kind of like the fireman's trick of stuffing a rope in a bag for use in rescue situations.
I use a swivel as a method to quick change from mono/flouro leader to steel leader and to minimize line twist.
Jeff
P.S. This sucks - 60 degrees in CT yesterday!!!