This 5-ingredient slow cooker flag day loin is the kind of set-it-and-forget-it supper that has fed Midwestern families for generations. You simply lay a raw center-cut pork loin roast in the crock, dump four familiar pantry ingredients over the top, and let it putter away all afternoon. By suppertime, the meat is fork-tender, the sauce is rosy and flavorful, and it tastes like you fussed all day, even though you barely lifted a finger. It reminds me of the easy holiday meals my mother threw together on busy farm days—simple, hearty, and the sort of thing that makes a husband go back for seconds without even asking.
Serve thick slices of the pork loin with a generous spoonful of the colorful sauce over the top. It’s lovely with mashed potatoes or buttered egg noodles to soak up the juices, plus a simple green vegetable like steamed green beans or peas. A crisp lettuce salad or coleslaw adds freshness, and warm dinner rolls or cornbread round things out. Leftovers make wonderful sandwiches on soft buns with a little extra sauce drizzled on and a few pickle slices alongside.
5-Ingredient Slow Cooker Flag Day Loin
Servings: 6-8

Ingredients
1 (3–4 pound) raw center-cut pork loin roast, trimmed if needed
1 cup ketchup
1/2 cup apple cider vinegar
1/2 cup packed light brown sugar
2 tablespoons yellow mustard
1 teaspoon salt (optional, to taste)
1/2 teaspoon black pepper (optional, to taste)
Directions
Place the raw center-cut pork loin roast in the bottom of a large slow cooker, fat side up if there is a fat cap. This helps baste the meat as it cooks.
In a medium bowl, whisk together the ketchup, apple cider vinegar, brown sugar, and yellow mustard until smooth and well combined. The sauce will be thick, glossy, and a pretty reddish color.
Taste the sauce and, if desired, stir in the salt and black pepper. This is optional but gives the pork a bit more depth and balance.
Pour the sauce evenly over the pork loin in the slow cooker, making sure the top of the roast is completely coated and some sauce runs down the sides. It should look like a colorful blanket of sauce over the raw meat.
Cover the slow cooker with the lid and cook on LOW for 6–8 hours, or on HIGH for 3–4 hours, until the pork is very tender and reaches an internal temperature of at least 145°F (63°C). For a shreddable texture, aim closer to 190–200°F (88–93°C).
Once cooked, carefully transfer the pork loin to a cutting board. Let it rest for about 10 minutes so the juices settle.
While the meat rests, skim any excess fat from the surface of the sauce in the slow cooker. If you prefer a thicker sauce, you can simmer it in a small saucepan on the stove for a few minutes or leave the lid off the slow cooker on HIGH for 15–20 minutes to reduce.
Slice the pork loin into thick slices or shred it with two forks, depending on how you like it. Return the meat to the slow cooker and gently toss with some of the sauce, or plate the meat and spoon the colorful sauce over the top.
Serve hot, passing extra sauce at the table so everyone can help themselves.
Variations & Tips
For a little more heat, add 1–2 teaspoons of crushed red pepper flakes or a dash of hot sauce to the ketchup mixture before pouring it over the roast. If you like a smokier flavor, stir 1–2 teaspoons of liquid smoke into the sauce, or substitute half of the ketchup with your favorite smoky barbecue sauce. You can also tuck a sliced onion under and around the pork before adding the sauce for extra sweetness and texture; the onions will melt right into the juices. For a slightly less tangy version, reduce the apple cider vinegar to 1/3 cup and increase the brown sugar to 2/3 cup. This recipe works best with a center-cut pork loin roast, but you can use a pork shoulder if you prefer a richer, more shreddable meat; just plan for the longer end of the cooking time. Always place the pork in the slow cooker raw and fully thawed—never frozen—to ensure even cooking. Use a meat thermometer to confirm the internal temperature reaches at least 145°F (63°C) in the thickest part of the roast, and refrigerate leftovers within 2 hours in shallow containers. Leftover pork and sauce will keep safely in the refrigerator for up to 3–4 days and can be reheated gently on the stove or in the microwave, adding a splash of water if needed to loosen the sauce.