Preheat the oven to 325 degrees F (165 degrees C).
Cut chuck roast into 3-inch cubes, removing excess fat and connective tissue. Season beef with salt and pepper.
Heat grapeseed oil in a large Dutch oven over high heat. Sear cubes of beef a few at a time, until well browned on all sides, about 4 minutes per batch. Reserve browned beef in a bowl. Reduce heat to medium and add onion and garlic. Cook until soft and just beginning to brown, about 10 minutes.
Add 1 cup beef broth to onion mixture and stir well; simmer for 1 to 2 minutes. Add beef and pour in guajillo sauce. Add a little beef broth to the empty jar, seal, and shake to release remaining sauce; pour over the beef. Pour in enough of the remaining broth to just cover the beef. Add bay leaves and bring to a gentle simmer.
Bake in the preheated oven, covered, until beef is fork-tender, about 2 1/2 hours.
Remove beef from sauce and set aside; discard bay leaves. Skim off excess fat from the top of the cooking liquid and bring to a boil to reduce slightly. Shred beef with two forks and return to cooking sauce.