01 - Rub beef cubes with kosher salt, black pepper, and dried thyme, coating all sides evenly.
02 - Transfer seasoned beef to the slow cooker insert. Top with chopped onion and minced garlic.
03 - Whisk together beef broth, Worcestershire sauce, tomato paste, and flour or cornstarch in a medium bowl until completely smooth and no lumps remain.
04 - Pour the liquid mixture over the beef and vegetables in the slow cooker. Stir gently to distribute ingredients evenly.
05 - Cover and cook on low setting for 6 to 7 hours, or on high for 3 to 4 hours, until beef is fork-tender and gravy has thickened.
06 - Taste the gravy and adjust seasoning if necessary. Serve over mashed potatoes, noodles, or rice, garnished with fresh parsley.