Pat beef dry and season with most of the salt and pepper. Brown in two batches in hot oil, leaving space around each piece, then transfer to the slow cooker.
Soften onion in the skillet for 4 minutes. Add garlic and tomato paste for 1 minute, then deglaze with 1/2 cup broth, scraping browned bits into the cooker.
Add remaining broth, Worcestershire, thyme, bay leaf, potatoes and carrots. Keep the lid in place and do not use frozen beef.
Cook on LOW for 7 to 9 hours or HIGH for 4 to 5 hours, until the beef separates easily with a fork and vegetables are tender.
Discard the bay leaf. Stir in the cornstarch slurry and peas, cover, and cook on HIGH for 15 to 25 minutes until the gravy lightly coats a spoon.
Taste for salt, rest uncovered for 10 minutes and skim excess surface fat if desired before serving.