Cut roast in half; place in a 5-qt. slow cooker. Sprinkle with the garlic, oil, salt and pepper. Add the onions, cilantro, salsa, broth, tequila and chiles. Cover and cook on low for 6-8 hours or until meat is tender. , Remove meat; cool slightly. Shred with 2 forks and return to the slow cooker; heat through. Spoon about 2/3 cup meat mixture onto each tortilla; serve with toppings of your choice.