Dredge the chuck roast in flour, salt, and pepper, and massage it into the meat.
In a skillet on a very high heat, brown the meat on all sides in the canola oil to create a crust.
Transfer the meat to a slow cooker and top with butter and pepperoncini.
Cover the slow cooker and set it to low.
In a small bowl, mix the mayonnaise, vinegar, dill, and paprika until well combined.
Spread over the meat, and cook on low for 8 hours.
Remove the roast and shred with two forks.
Return meat to the slow cooker, and stir to mix in the juices. Serve with fresh parsley.
