Dredge the chuck roast in flour, salt, and pepper to taste, 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 Crock-Pot and top with butter and pepperoncini. Cover the slow cooker and set it to Low setting.
In a small bowl, mix the mayonnaise, vinegar, dill, and paprika until well combined, open the slow cooker and spread this over the meat, cover, and cook on low for 8 hours.
Remove the roast and shred with two forks, then return the meat to the slow cooker, and stir to mix in the juices. Serve garnished with fresh parsley, and sides of your choice.