Place Pork Belly in large, resealable bag. Mix together water, oyster sauce, ginger root, 2 tablespoons cilantro and the garlic in small bowl. Pour marinade mixture over pork belly; close bag to seal. Turn bag to evenly coat pork belly with marinade. Refrigerate for 24 hours, turning bag occasionally.
Preheat oven to 300 degrees F. Remove pork belly from marinade; discard marinade in bag. Place pork belly on rack in Dutch oven. Bake, covered, about 4 hours or until tender. Transfer pork belly to plate; discard fat. Cover and refrigerate pork belly until firm.
Just before serving, cut chilled pork belly into 2 ounce slices. Place slices in a single layer in a large skillet. Cook, uncovered, over medium-low heat for 8-10 minutes or until lightly brown and crisp on both sides. If necessary, spoon and discard drippings in skillet if splattering begins.
Meanwhile, just before serving, in a medium bowl mix cilantro, red onion and scallions. Combine rice vinegar, sesame oil and salt; pour over cilantro mixture and toss until evenly coated.
To assemble, place tortillas on dinner plate, slightly overlapping. Cover with damp paper towel. Microwave on HIGH about 30 seconds or until warm. Brush one side of tortillas with hoisin sauce. Place hot pork belly slices on top of tortilla. Top with cilantro slaw and serve like an open faced taco.