Sear the beef in olive oil until browned on all sides; set aside.
In the same skillet, sauté onion, carrots, and celery until softened. Add garlic and mushrooms; cook until fragrant.
Stir in flour and gradually add beef broth while scraping the bottom of the pan to deglaze.
Combine seared beef with the vegetable mixture in your slow cooker. Add apple cider vinegar, tomato paste, herbs, potatoes, salt, and pepper.
Cook on low for 6-8 hours or high for 3-4 hours until beef is fork-tender.
Helpful Notes:
For added flavor, consider incorporating seasonal vegetables like parsnips or turnips. You can also experiment with fresh herbs to enhance the dish further.