Preheat oven to 300 degrees.
Sprinkle salt over the roast then dust evenly with flour, rubbing around to even consistent coverage.
Add 2 tablespoons of oil to Dutch oven set to medium-high heat. Once oil is hot and shimmering add roast and sear on all sides until a brown crust forms.
Remove roast from the pot, reduce heat to medium low, and add additional tablespoon of oil. Add onions and slowly saute until golden brown and caramelizing, ~15 minutes or longer. Add garlic and saute additional 2 minutes.
Increase heat and add a few splashes of beef broth and scrape brown bits from the bottom of the pot to incorporate into liquid, then add all ingredients to the pot.
Cover Dutch oven, bring to a simmer and place in the oven. Braise for 3 hours or until beef can easily be shredded with a fork.
Slice or shred beef and serve on plates with the potatoes, onions, and juices.