To make the gravy, strain the juice into a large sauce pan. Remove the strainer and contents. Place the pan over medium-high heat and bring it to a low boil. In a large measuring cup, add 1½ cups of water and 3 tablespoons of cornstarch. Mix until combine. Slowly add the cornstarch mixture to the boiling turkey juices, stirring constantly until the mixture thickens and becomes semi-translucent.