Heat the oil in a large skillet over medium-high heat until smoking. Meanwhile, season the pork roast with salt and pepper, then dredge in flour, and shake off excess. Sear in hot oil until browned on all sides, about 1 minute per side.
Place onto a large sheet of aluminum foil set on top of a baking sheet; set aside. Stir together the maple syrup, ketchup, water, and garlic. Pour 3/4 of this sauce over the pork. Fold the foil over the pork, and seal to form a packet.
Bake in preheated oven until the internal temperature reaches 170 degrees F (75 degrees C), about 2 hours. Carefully open up the foil packet, and broil for a few minutes until the sauce glazes the meat. Serve with remaining sauce.