To cook pre-browned prime rib in a slow cooker, cook a 3 pound rib roast for about six hours with five cloves of garlic and a teaspoon each of oregano, liquid smoke and Worcestershire sauce. Parsley, 2 tablespoons of ground mustard and 1/4 teaspoon of thyme are also needed.
First take all the ingredients except the rib roast and place them into a food processor. Set the machine to pulse and combine the ingredients until they form a paste. In a large skillet, heat 1 tablespoon of olive oil and add the rib roast after seasoning it all over. Brown the meat on all sides, then transfer to a waiting platter. Rub the herb paste generously over the surface.
Place the roast into the slow cooker and cook for approximately six hours. After that time, take a meat thermometer and check the center for the desired level of doneness. Rare meat is roughly 115 degrees Fahrenheit, medium-rare 120 to 130 degrees, medium 140 degrees, medium-well 150 degrees and well done meat will measure above that. When the meat is done, remove it from the slow cooker and place on a platter or cutting board, covering it loosely with aluminum foil and allowing it to rest for at least 10 minutes before slicing. Serve with the juices collected in the bottom of the slow cooker or with classic horseradish sour cream.