Toss the beef with flour, salt, and black pepper until evenly coated, then shake off any excess flour for a cleaner sear. Brown the beef in batches in a preheated Dutch oven with olive oil over medium-high heat until deeply browned on the outside, about 3-4 minutes per batch.

Transfer the browned beef to the slow cooker as each batch finishes. Keep the heat steady so the next batch browns quickly rather than steaming.

In the same Dutch oven, cook the diced onion, minced garlic, and tomato paste for 3 minutes over medium heat, stirring until the tomato paste darkens slightly and smells fragrant.

Pour in the dry red wine and scrape up the browned bits from the bottom, then simmer for 3 minutes until the liquid is slightly reduced and looks glossy. Pour this mixture into the slow cooker.

Add the beef broth, balsamic vinegar, rosemary, thyme, carrots, and frozen pearl onions to the slow cooker, then stir gently to combine.

Cover and cook on LOW for 8 hours until the beef is very tender and falls apart when pressed with a fork, and the carrots are soft.

Remove the rosemary and thyme herb stems, then taste and adjust seasoning if needed. Serve the wine-braised stew over creamy polenta or mashed potatoes so the sauce coats the base.