Combine all the "dry mix" ingredients in a small bowl and mix. Set aside. (Dry mix includes corn starch, garlic powder, broth powder, chopped onions, salt, and pepper.)
Set chuck roast on the bottom of the slow cooker.
Spread ranch powder over the top.
Spread "dry mix" over the top.
Set a stick of butter on the middle of the roast.
Place peperoncinis around the stick of butter, on top of the roast.
**Do not add water to this recipe.**
Cook in the slow cooker for 8 hours on low. Never open the lid while cooking.
Pull roast into serving dish to rest. Slice as desired, and add back flavorful juices from the slow cooker as desired. The peperoncinis can be discarded or eaten (we like to eat them because they're tasty).