Seasoning the beef. Mix all the seasoning rub ingredients and generously season the beef roast. Set aside while preparing other ingredients.
Prepare the vegetables and toss them inside the Crock Pot or Instant Pot.
Searing the beef. Preheat a grill or cast iron pan. Grease the grill or cast iron pan with cooking oil. Sear the beef roast for about a minute on each side or until browned.
Place the seared beef in the Crock-pot or Instant Pot with the vegetables.
Add the crushed bouillon cube, Worcestershire sauce, red wine(optional), and the slurry (water and flour).
Cook on low and slow. Cover with the lid on, and slow cook on low for about 7 to 8 hours.
Remove the slow-cooked beef and cover to rest while thickening the gravy.
To make the gravy. Place a strainer on a saucepan to remove and strain the vegetables from the Crock Pot. If using an Instant Pot, use a slotted spoon or spider spoon to remove the vegetables. Bring to a simmer until thickened to your desired consistency. Add a slurry (flour mix in water or broth) if needed.
Serving the slow cooker Pot Roast. Shred the beef with a fork. Serve with the carrots from the pot roast or potatoes, if added. And classic side dishes for pot roast, like mashed potato and steamed beans. Pour the gravy over the shredded beef.