Combine the chicken breasts, diced tomatoes, half of the chicken stock, chili powder, salt, cumin, and oregano in the bowl of a slow cooker. Make sure the chicken is covered, and add additional stock if needed. Cover with the lid and cook on high for 2 hours.

Meanwhile, peel the sweet potatoes. Spiralize them with Blade D. Then, transfer the sweet potato noodles to a food processor and pulse until rice-like, working in batches. Rice all of the sweet potato noodles and set aside.

Remove the lid and add the sweet potato rice, black beans, frozen corn, and the remaining chicken broth. Replace the lid and continue cooking on high for another 2 hours. Cooking is done when the rice is tender.

Using tongs, remove the chicken from the slow cooker and shred, using two forks. Add the shredded chicken back in and stir to combine. Taste and adjust the seasoning, if needed.

Divide the burrito mixture into bowls and top with cilantro, avocado, and scallions.