Preheat oven to 300° F.

Season roast heavily with salt and pepper.

Heat oil in a Dutch oven.

Sear roast for a couple minutes on each side over medium-high heat, until nicely browned. Transfer roast to large plate.

Add onion and garlic to the pot, stirring over medium heat until onions are soft.

Stir in flour and tomato paste, followed by stock and Worcestershire sauce.

Stir and scrape browned bits from bottom of pot.

Add roast back to pot, cover tightly and place in oven. (Optional: transfer roast and liquid to a slow cooker, cover and cook on low 6 to 7 hours until tender.)

Cook for 3 hours, turn roast, add rosemary and cook approximately one more hour, until completely tender.

Transfer roast to cutting board and tent with foil. Remove rosemary and, using a ladle, skim fat from liquid.

Place Dutch oven on stovetop and bring contents to a boil.

Slice pot roast against the grain or pull in bite-size pieces. Serve with reduced sauce.