Cut roast into large 2 - 2 1/2" chunks. Trim excess fat while prepping.
Cut unpeeled carrots into 2 inch pieces and cut onion into eighths.
Place beef pieces in bowl, salt & pepper aggressively and sprinkle with brown sugar. Allow beef to rest for a few minutes if time permits.
Preheat oven to 275 degrees F.
Heat 2 tablespoons oil in heavy dutch oven over medium high heat until the oil shimmers. Brown beef in three batches, making sure all sides of the beef cubes are seared. Remove beef to platter.
Add remaining 2 tablespoons of oil to pan to heat. Add carrot and onion and cook over medium high heat for 4 to 5 minutes until slightly browned. Sprinkle flour over vegetables then stir and cook for another 2 - 3 minutes.
Add Guinness to pan and scrape brown bits from bottom. Add beef broth and return beef to pan. Bring to a boil. Once beef comes to heat, cover tightly with lid, and place in preheated oven. Cook for at least 3 hours, checking occasionally that the juice is holding up.
If the gravy is too thin, remove the lid from the pan and turn up the heat to 350 degrees F for the last half hour of cooking.