Season the beef short ribs generously with salt and pepper on all sides.
In a large skillet over medium-high heat, sear the ribs for 2-3 minutes on each side until browned. This step adds depth to the flavor but can be skipped if you prefer a quicker method.
In the bottom of the crockpot, add the chopped onion, minced garlic, carrots, and celery.
In a separate bowl, mix the beef broth, crushed tomatoes, brown sugar, soy sauce, Worcestershire sauce, smoked paprika, and dried thyme. Stir well until combined.
Place the seared short ribs on top of the vegetable layer in the crockpot and pour the sauce mixture over everything. Ensure the ribs are mostly submerged.
Cover and cook on low for 8 hours or high for 4-5 hours, until the meat is tender and falling off the bone.
Once cooked, gently remove the ribs and vegetables from the crockpot. You can thicken the sauce by leaving it on high for an additional 15 minutes with the lid off.
Serve the ribs on a platter with a drizzle of the sauce and garnish with fresh parsley.
Notes
Searing the ribs is optional but enhances the flavor.