How to Make It
Stir together first 6 ingredients in a 7-qt. slow cooker; stir in 2 tsp. salt and 1/2 tsp. pepper. Cover and cook on LOW 8 hours.
Meanwhile, place ground chuck and ground pork in a large bowl. Add next 6 ingredients and remaining 1 Tbsp. salt and 1/2 tsp. pepper; mix gently just until blended. Gently shape mixture into 24 meatballs. (Do not pack.) Place meatballs in a single layer on a baking sheet; cover well, and chill until ready to use.
Let meatballs stand at room temperature 20 minutes. Carefully submerge meatballs in tomato mixture in slow cooker. Cover and cook on HIGH 1 hour or until meatballs are done, stirring after 30 minutes.
Preheat broiler with oven rack 7 inches from heat. Arrange bottom halves of 12 buns in a single layer on each of 2 baking sheets. Place 1 meatball on each bun; top with sauce and 1 halved provolone cheese slice. Repeat with remaining buns, meatballs, and cheese.
Broil sliders, 1 baking sheet at a time, 2 to 3 minutes or until cheese melts. Top with top halves of buns.