Use paper towels and pat beef dry with them. Gently drizzle up salt and pepper all over it.
Take a skillet and heat oil over high heat flame. Let it get brown all over intensely - The flavour base gets best with a deep dark brown crust! This will take about 7 minutes.
Shift the beef into a slow cooker.
In the same skillet, pour garlic and onion. Cook until onion is browned, for 2 minutes.
Stream the wine, decrease it by half quantity. Shift to a slow cooker.
Blend flour with 1 cup of the broth. If there are lumps, it is all ok. Stream it into a slow cooker.
Take a slow cooker and pour leftover celery, rosemary, broth, carrots, and thyme.
Cook the slow cooker on LOW for 5 hours after properly covering it.
Afterward, add up some potato, cook on LOW for 3 hours.
Take out the beef. Give it rest of 5 minutes, slice it thickly.
Taste it and adjust salt and pepper as per your taste.
Serve the slow cooker roast beef along with delicious vegetables and a dash of savoury sauce!