Brown and drain ground beef well to avoid a greasy casserole and enhance flavor., Cut potatoes uniformly (about 1 inch) for even cooking and to prevent falling apart., Always place potatoes on the bottom for optimal cooking since they need the heat source., Do not overfill the slow cooker; fill no more than two thirds full for even cooking and proper lid sealing., Add 1/4 to 1/2 cup water or low-sodium broth if tomato sauce is very thick or liquid is insufficient., Avoid lifting the lid during cooking to prevent heat loss and extended cooking time., For a browned cheese top, after slow cooking, transfer casserole to an oven-safe dish and broil briefly., Adjust salt and pepper after cooking as flavors concentrate during slow cooking., When using lean ground turkey or chicken, add a tablespoon of oil when browning to prevent dryness., The casserole can be assembled the night before and refrigerated; allow the insert to sit at room temperature for 15–20 minutes before cooking., Cool completely before freezing; freeze up to three months. Thaw overnight in fridge and reheat until center reaches 165°F (74°C)., Potatoes may soften slightly after freezing and thawing; flavor remains great., For dairy-free option, use dairy-free cheese and skip sour cream. Increase seasonings slightly to compensate., Ensure seasonings and tomato sauce are gluten-free if needed., Leftovers keep refrigerated for up to 3 days in airtight container; reheat via microwave, oven, or slow cooker.