Generously season the roast with salt and pepper.
In a large skillet, melt 1 tablespoon of butter over medium high heat. Add the seasoned roast and brown on 2 or more sides for several minutes on each side. Transfer roast to a 6-quart sized or larger slow cooker.
Pour beef broth into the slow cooker and add the onions, carrots, garlic cloves, and herbs.
Cover slow cooker with lid and cook on high for 4-5 hours or on low for 6-8 hours, or until roast shreds easily with a fork.
Remove roast from slow cooker and cover to keep warm.
Dump the broth and vegetables through a strainer, reserving the broth. Use a spoon to skim as much fat off the top of the broth as possible. Set aside vegetables to serve with roast.
To make gravy, add the remaining tablespoon of butter to a skillet set over medium heat. Once melted, add the flour and whisk together. Add the broth to the skillet and whisk constantly until smooth. Bring to a boil and continue to whisk until thickened, about 2 minutes.
Shred roast and serve with gravy over mashed potatoes, or as desired.