Cut and season the beef: Cut the chuck roast into 3–4 large chunks.
Pat dry. Season all sides with salt and pepper.
Brown for flavor: Heat oil in a large skillet over medium-high. Sear beef on all sides until deeply browned, about 2–3 minutes per side.
This step adds big flavor.
Layer the slow cooker: Add sliced onion and minced garlic to the bottom of the slow cooker. Place browned beef on top.
Mix the sauce: In a bowl, whisk beef broth, chipotle, adobo sauce, tomato paste, lime juice, apple cider vinegar, cumin, chili powder, smoked paprika, oregano, and coriander if using.
Combine and cook: Pour the sauce over the beef. Tuck in bay leaves.
Cover and cook on Low for 8–10 hours or on High for 4–5 hours, until the beef is fork-tender.
Shred the beef: Remove bay leaves. Transfer beef to a board and shred with two forks. Skim excess fat from the cooking liquid if needed.
Moisten and adjust: Return shredded beef to the slow cooker and toss with the juices.
Taste and adjust salt, lime, or heat as needed.
Serve: Spoon into lettuce wraps or low-carb tortillas, or build bowls with cauliflower rice, avocado, and fresh cilantro. Add a squeeze of lime.