Prep the slow cooker. Lightly grease the insert with a bit of olive oil or cooking spray to prevent sticking.
Season the chicken. In a small bowl, mix chili powder, cumin, garlic powder, onion powder, smoked paprika, salt, and pepper. Sprinkle evenly over both sides of the chicken.
Add to the crockpot. Place the seasoned chicken in the slow cooker.
Pour the salsa and lime juice over the top. Drizzle in the olive oil if using.
Cook low and slow. Cover and cook on Low for 4–6 hours or High for 2.5–3.5 hours, until the chicken is tender and easily shreds with two forks.
Shred the chicken. Transfer the chicken to a cutting board and shred with forks. Return it to the crockpot and stir into the salsa sauce to soak up the flavor.
Adjust and finish. Taste and add more salt, lime juice, or a pinch of sugar if your salsa is very tangy.
Stir in chopped cilantro if you like.
Serve your way. Use for tacos, burrito bowls, salads, nachos, quesadillas, or stuffed sweet potatoes. Spoon extra sauce over the top for moisture.