Place the boneless chicken thighs in the slow cooker. Pour the green salsa over the top, ensuring the chicken is fully coated.
Cover the slow cooker and cook on low for 6 hours or until the chicken is tender and easily shredded.
Once the chicken is cooked, use two forks to shred the meat directly in the slow cooker. Mix well to combine with the salsa.
In a large skillet, add the black beans and corn, heating them over medium heat until warmed through. Season with salt and pepper to taste.
To assemble the burritos, lay a tortilla flat and add a generous scoop of the shredded chicken mixture, followed by the black beans, corn, and a sprinkle of cheddar cheese and chopped cilantro.
Fold in the sides of the tortilla and roll it up from the bottom to the top, creating a burrito. Repeat with the remaining tortillas and filling.
Optionally, warm the assembled burritos in the tortilla warmer or wrap them in aluminum foil and place them in a preheated oven (300°F/150°C) for 10 minutes to melt the cheese.
Serve the burritos with sliced avocado and lime wedges on the side.