There are two ways you can make this casserole in advance. The first way is you can prep all the ingredients and pour them into the crockpot. Then cover and store in the fridge for up to 24 hours. Then when you are ready to cook, place it in the crockpot and turn it low. You will need to add extra cook time since you are starting to cook from a cold pot. The second way is to cook it fully, then transfer it to an airtight container. Then reheat the next day, or leave it in the crockpot and warm it up the next day.