Put the beef in a slow cooker with a jar of pepperoncini and the juice. If you like, cut the stems off the pepperoncini. If there isn't enough juice, add some beer.
Cover, set to low, and let it cook for several hours until the meat falls apart when poked with a fork.
Shred the meat. If you like, chop up a few of the pepperoncini.
Serve meat on rolls with mayo if you like. Lay sliced provolone over the meat and slide it under the broiler to toast the bread and melt the cheese. Serve the juice on the side for dipping.