Season the beef cubes with salt and pepper.

In a large skillet, heat olive oil over medium-high heat. Brown the beef in batches, transferring to the slow cooker as they are done.

In the same skillet, add the bacon and cook until crispy. Remove and add to the slow cooker.

Add the onion, carrots, and garlic to the skillet. Cook until the onion is translucent, then stir in the tomato paste.

Pour in the red wine, scraping up any browned bits from the bottom of the skillet. Bring to a simmer, then transfer to the slow cooker.

Add the beef broth, Worcestershire sauce, thyme, and bay leaves to the slow cooker. Stir to combine.

Cover and cook on low for 8 hours or until the beef is tender.

About 30 minutes before serving, add the mushrooms to the slow cooker.

To thicken the sauce, mix the flour with a bit of water to form a slurry and stir it into the slow cooker. Cook for an additional 30 minutes.

Remove bay leaves, garnish with fresh parsley, and serve.

For a gluten-free version, substitute the all-purpose flour with cornstarch or a gluten-free flour blend. If you prefer a richer sauce, add a tablespoon of butter at the end of cooking. For a different flavor profile, try adding a tablespoon of balsamic vinegar or a splash of brandy. Vegetarians can substitute the beef with hearty vegetables like eggplant or portobello mushrooms and use vegetable broth instead of beef broth.