Dice the beef into 1-inch cubes and set aside. Dice all 3 onions into roughly equal pieces, mince the 3 garlic cloves, and cut the potatoes into 1-inch chunks. Cut the 5 carrots and 3 celery stalks into similar-sized pieces (about 1-inch). This uniform sizing ensures everything cooks evenly. Measure out your beef broth, Worcestershire sauce, and prepare the cornstarch slurry by mixing 2 tablespoons cornstarch with 2 tablespoons cold water in a small bowl—set this aside for later.

Heat 1.5 tablespoons of oil in a large pot or Dutch oven over medium-high heat until it shimmers. Working in batches if needed, brown the diced beef on all sides, about 3-4 minutes per batch, then transfer to your slow cooker. Don't overcrowd the pan—proper browning develops deep flavor through the Maillard reaction, which is essential for a rich stew. I always make sure not to move the meat around too much while it's searing, as this helps develop a proper golden crust.

In the same pot you used to brown the beef, add the diced onions and cook over medium heat for about 5-7 minutes, stirring occasionally, until they become soft and translucent. Add the minced garlic and cook for another 1 minute until fragrant. Pour in 1/2 cup of the beef broth and use a wooden spoon to scrape up all the browned bits (fond) from the bottom of the pot—this concentrated flavor is liquid gold for your stew. Pour this entire mixture into the slow cooker with the beef.

Add the potatoes, carrots, and celery to the slow cooker with the beef and aromatics. In a separate bowl, whisk together the remaining 4 cups of beef broth, 1.5 tablespoons Worcestershire sauce, and 5 tablespoons flour until completely smooth—the flour acts as a thickening agent and creates a silky sauce. Pour this mixture over everything in the slow cooker, then add the thyme sprig, rosemary sprig, and bay leaves. Stir well to combine and ensure the flour is evenly distributed.

Cover the slow cooker and cook on LOW for 7-8 hours, or on HIGH for 4 hours, until the beef is very tender and the vegetables are cooked through. The long, gentle heat allows the tough beef cuts to become fork-tender while the flavors meld together beautifully.

Remove the lid and stir in the cornstarch slurry from Step 1, which will thicken the broth into a rich, silky sauce. Replace the lid and cook on HIGH for 15-30 minutes without the lid, stirring occasionally, until the sauce reaches your desired thickness. I find that checking it after 15 minutes helps you avoid over-thickening—you want it thick enough to coat a spoon but not gluey. Taste the stew and adjust seasoning with additional salt and pepper if needed, then remove the herb sprigs and bay leaves before serving.