Amazing Slow-Roast Cooker BBQ Beef Sandwiches

Ingredients

• 1 Tablespoon vegetable oil
• 1 3-pound boneless beef shoulder or chuck roast
• 1 cup barbecue sauce
• 1/2 cup cider vinegar
• 1/2 cup chicken broth
• 1/4 cup packed brown sugar
• 1 Tablespoon prepared mustard
• 1 Tablespoon Worcestershire sauce
• 1 Tablespoon chili powder
• 1/2 medium yellow onion minced
• 2 garlic cloves crushed
• 1 1/2 teaspoons dried thyme
• 6 to 8 hamburger buns
• Butter optional
• 6 to 8 slices Swiss cheese optional