Rinse and pat dry the chicken breasts. Lightly drizzle with olive oil.
Sprinkle the chicken breasts with the taco seasoning rubbing into the chicken on all sides.
Spray the liner of a 6 quart oval slow cooker with cooking spray. Arrange the seasoned chicken breasts in a single layer on the bottom. Drizzle with additional olive oil.
Pour the tomatoes evenly on top and sprinkle with garlic salt.
Cover and cook on low for 5 hours or on high for 3-4 until the chicken is fork tender.
Using 2 forks. pull the chicken pieces apart, and gently stir into the sauce.
To thicken the sauce add 1 Tbsp of tomato paste at a time ands gently mix through.. Repeat until the sauce has thickened to your preference..
Serve on warm tortillas with your favorite taco toppings.