You can lay the rat out to thaw until room temp or soft all the way thru ... Then you can either put the rat in a zip lock bag and then let sit in hot water, or set it under a heat lamp , some people even prefer to use a hair dryer to heat up the rat .... Important thing is that the rat is around 95 to 100℉ when you offer it, you'll want to be sure to use some tongs as well to ensure he doesn't accidentally nab you when going for the feeder