Add 2 Tbs oil to a pan. Sprinkle roast with 2 Tbs flour, one on each side, sprinkle with a pinch of salt, pepper, and then pat on 1 clove fresh garlic on roast as well, then sear. Set roast in slow cooker.
Add 1 Tbs of oil and 1 tbs of butter to same pan. Then add sliced mushrooms, onion and other clove of garlic to pan. Sauté for 5 min. On med. high heat. Then add tomato paste and 1 Tbs flour. Using a flat spatula, pat down paste and mix up, then add broth, continue mixing until blended. Set aside.
Add potatoes, carrots and celery around roast in slow cooker. Then pour broth and mushroom mixture over roast. Add Bay leaf. Sprinkle 1 tsp of pepper and dash of salt on top. Cover and cook for 6 hours on low or longer if you like it falling apart.
When roast is done, take a soup spoon and put liquids from roast in a pan on the stove (you don't need all liquids just the most you can get easily by moving roast and veggies aside. Then in a small bowl, mix 1 Tbs of cornstarch with a few Tbs of the juices until starch is blended. Add to juices and cook on med low until thickened about 10 minutes., stirring frequently. Serve with gravy on top of meat.