I've got an upright freezer in the garage, so I empty out the bottom rack (or two) and line the bottom with 2-3 layers of plastic bags, or a good 2mil drop cloth...
Then I'll just throw the hide in the freezer for a day or two. No bags until after I know the whole thing is cooled.
Dunno if it's right or wrong (as I've only needed to do it twice)...but it works.