Season the beef short ribs with salt and black pepper.
In a large skillet, heat the olive oil over medium-high heat and sear the short ribs on all sides until browned, about 3-4 minutes per side.
Transfer the ribs to the crockpot.
In the same skillet, add the chopped onion and minced garlic, and sauté for 2-3 minutes until the onion is translucent.
Pour in the beef broth, red wine, Worcestershire sauce, brown sugar, tomato paste, dried thyme, and bay leaves. Stir to combine and bring to a simmer.
Pour the sauce mixture over the short ribs in the crockpot.
Cover and cook on low for 8 hours or on high for 4 hours, until the meat is tender and falling off the bone.
Once cooked, remove the short ribs from the crockpot and let them rest for a few minutes. Discard the bay leaves.
If desired, skim excess fat from the sauce and serve it alongside the ribs.