If desired, heat olive oil in a skillet over medium-high heat. Season chicken breasts with salt, pepper, chili powder, cumin, garlic powder, and onion powder. Sear chicken on both sides for 2-3 minutes until golden brown. This step enhances flavor through browning.

Transfer the chicken to the slow cooker. Pour chicken broth and salsa over the chicken. This will keep the chicken moist and flavorful while it cooks.

Cover the slow cooker and cook on low for 6-8 hours or high for 3-4 hours. The longer cooking time allows the chicken to become tender and easily shred.

Once cooked, remove the chicken from the slow cooker and shred it using two forks. Return the shredded chicken to the slow cooker and mix it with the juices. This ensures the chicken is well-coated and flavorful.

Warm the tortillas in a dry skillet or microwave until pliable. This prevents them from cracking when filled.

Spoon the shredded chicken mixture onto each tortilla. Top with shredded lettuce, diced tomatoes, cheese, sour cream, and cilantro as desired.

Serve immediately while warm, allowing everyone to customize their tacos to their liking.