The best way to defrost frozen flats of bait , we are always thawing frozen 50 pound flats of fish, this method  works the best.Get a large bean sack ,they also use these for storing gillnets ,cinch the top with a dock line cleat it off and through it in the water ,when it is defrosted you will start to hear the rope creek dump it out and you will have clean thawed bait to cut in your ChumCutter . In 64 degree water it only takes 20 minutes or so  to defrost a flat so we only defrost what were going to use. The other flats stay in the cooler and go back in the freezer if we don’t use them.  .Steve Corbett