Season beef generously with salt and pepper.
Heat olive oil in a skillet and sear beef on all sides until browned.
Place sliced onions and garlic in the slow cooker.
Add seared beef on top of onions.
Whisk BBQ sauce, beef broth, Worcestershire sauce, brown sugar, paprika, and chili powder.
Pour sauce mixture over beef.
Cover and cook on LOW for 8 hours or HIGH for 4–5 hours.
Remove beef and shred using two forks.
Return shredded beef to slow cooker and mix with sauce.
Serve warm on slider buns.