Inspired by Italian roast pork sandwiches we’ve had in Philadelphia, this weeknight version uses a slow cooker to develop loads of flavor and create meltingly tender meat. The sandwich is then quickly built with provolone, arugula for a peppery bite and Giardiniera for that extra pickle-like punch to cut through the rich roast pork.
Season the pork generously with salt and pepper and rub all over with the fennel seeds. Transfer to a 6- to 8-quart slow cooker and add the rosemary, bay leaf, garlic and olive oil. Cover and cook on low until the meat is browned in spots and tender, 7 hours.
Pull the pork apart with tongs or 2 large forks. Discard any large chunks of fat and discard the rosemary and bay leaf. Toss the meat in the juices; season with salt and pepper.
Cut the bread crosswise into 4 pieces and split each piece open. Toast the bread, if desired. Divide the cheese among the bottom halves of the bread, then top with the meat, leaving the juices in the slow cooker. Top the sandwiches with the giardiniera plus a drizzle of giardiniera brine, the pepperoncini and arugula.
Strain the juices from the slow cooker into a liquid measuring cup, then pour into small ramekins or cups. Serve with the sandwiches for dipping.