Season the chuck roast generously on all sides with salt and pepper.
Heat olive oil in a large skillet over medium-high heat and sear the roast for 3-4 minutes per side until deeply browned.
Place the quartered onion, carrots, potatoes, and celery in the bottom of your slow cooker.
Transfer the seared roast on top of the vegetables.
In a bowl, whisk together beef broth, tomato paste, minced garlic, and dried thyme, then pour over the roast.
Add bay leaves to the liquid and cover the slow cooker.
Cook on low for 8 hours or high for 5-6 hours until the meat is fork-tender.
Remove bay leaves, slice or shred the roast, and serve with the vegetables and cooking liquid as gravy.