In slow cooker, add stock, pepperoncini peppers, onion, garlic, Italian seasoning, onion powder, and bay leaf; stir to combine. Transfer roast into slow cooker. Cover and cook on low 7-8 hours.

Remove lid and reduce to warm heat. Drain 3-4 cups of liquid into bowl, skim off fat, and strain to remove any solids. Simmer 4-5 minutes, then transfer mixture to serving bowl.

Shred beef using two forks and arrange on platter. Then, add onions, pepperoncini peppers, discarding any stems, and layer of cheese.

Serve with reduced liquid as dipping sauce.