Place the chicken breasts in the slow cooker and sprinkle evenly with the taco seasoning and ground cumin.
Pour the rinsed black beans over the chicken, then spoon the chunky salsa on top.
Cover and cook on LOW for 4 hours, or until the chicken is tender and easily shreds with two forks.
Remove the chicken to a cutting board and shred with two forks, then return the shredded chicken to the slow cooker and stir to combine with the beans and sauce; keep warm.
Divide the chopped lettuce among four plates (about 1 1/2 cups each).
Top each portion of lettuce with about 3/4 cup of the chicken-and-bean mixture, sprinkle with 1 tablespoon cheese, and drizzle with 2 tablespoons dressing.