Here's an easy way to do it - line your baking pan with foil with some overhang (roll up during baking), then place your ingredients and bake. After it's completely cool, wrap and place in freezer in baking dish. When frozen, you can just plop out the frozen food (I place it in a plastic bag) and take your baking pan out to use again. Then, when defrosting and reheating, you can just stick the food back in the same pan.