Heat the olive oil in a large skillet over medium heat. Add the sliced onions and cook, stirring often, until they turn golden and soft, about 10 minutes.
Add the beef stew meat to the skillet and brown it on all sides for 5 minutes. Sprinkle in the flour and stir to coat the meat and onions.
Transfer the mixture to the slow cooker. Add the potatoes, carrots, garlic, thyme, Worcestershire sauce, salt, and pepper.
Pour the beef broth over everything and stir gently to combine.
Cover and cook on low for 8 hours until the beef is tender and the gravy has thickened.
Taste and adjust salt and pepper before serving.