Combine the salt, pepper, and flour in a small bowl.
Coat the beef with the flour mixture, making sure it is covered entirely.
Heat oil in a large skillet. Sear the meat on each side until it’s golden brown.
Transfer the meat into the slow cooker, then add the celery, red onion, carrots, canned tomatoes, garlic, wine, sage, parsley, bay leaf, and salt.
Cook the beef stew on low heat for 8 hours.
Serve it with your desired side dish (e.g. couscous, soft polenta, mashed potatoes) and sprinkle some freshly chopped parsley. Enjoy!