In a large skillet, heat the olive oil over medium-high heat. Add the beef cubes and brown on all sides, about 5-7 minutes. Transfer the browned beef to the slow cooker.

In the same skillet, add the chopped onion and minced garlic. Sauté for 2-3 minutes until the onion is translucent. Add to the slow cooker.

Add the sliced carrots, diced potatoes, beef broth, frozen peas, tomato paste, Worcestershire sauce, thyme, rosemary, salt, and pepper to the slow cooker. Stir to combine.

Cover and cook on low for 8 hours or on high for 4 hours, until the beef is tender and the vegetables are cooked through.

If you prefer a thicker stew, mix the cornstarch and water in a small bowl until smooth, then stir it into the stew during the last 30 minutes of cooking.

Taste and adjust seasoning if necessary before serving.