Combine all remaining ingredients in a 6qt slow cooker.
Cook on low for 5-6 hours.
Top with remaining French-fried onions and serve.
Notes
For a thicker sauce, take the lid off the Crock Pot half an hour before it is finished cooking to allow some moisture to escape.Keep leftover crock pot green bean casserole covered in the refrigerator for up to 4 days and reheat on the stove or in the microwave.Freeze portions in zippered bags for up to 4 weeks.