Place chicken thighs in 3 1/2 or 4-quart slow cooker. Sprinkle with garlic, roasted pepper strips and salt.
Cover; cook on Low setting for 6 to 7 hours.
Just before serving, remove chicken from slow cooker; place on large plate. Shred chicken with 2 forks; return to slow cooker and mix well.
In small bowl, combine mayonnaise and pesto; blend well. Cut focaccia into 6 wedges; split each in half. Spread cut sides with mayonnaise mixture. With slotted spoon, place about 1/3 cup chicken mixture onto bottom half of each focaccia wedge. Top each with tomato slice and top half of focaccia.