Cut the beef chuck roast into 1-inch cubes, trimming any excess fat. Season generously with garlic salt and pepper, then sprinkle flour over them, tossing to coat evenly.

In a large skillet, heat olive oil over medium-high heat. Add the seasoned beef in batches, browning for about 3-4 minutes per side.

Transfer the browned beef to the slow cooker, keeping any juices in the skillet.

In the same skillet, reduce heat to medium and melt butter. Add diced onions and sauté until translucent, then add minced garlic for an additional minute.

Deglaze the pan with red wine, scraping up the browned bits. Pour this mixture over the beef in the slow cooker.

Add beef stock, carrots, potatoes, bay leaves, and rosemary to the slow cooker. Stir gently to combine.

Cover and cook on low for 7.5-8 hours or high for 3.5-4 hours.

About 15 minutes before serving, mix in the green peas.

If you prefer a thicker stew, mix cornstarch with cold water to create a slurry and stir into the stew during the last 10 minutes.

Just before serving, stir in a tablespoon of cold butter to enrich the stew.

Ladle into bowls and serve warm.