Place the chicken, potatoes, carrots, and onions into the slow cooker. In a bowl, mix together the tomato sauce, sofrito sauce, garlic, chicken stock, oregano, cumin, and sazon seasoning.
Pour the mixture over the chicken and vegetables. Drop the olives over the top. Cover the slow cooker and cook on low for 7 hours.
If desired, remove the chicken and shred it prior to serving, or serve with the chicken in whole pieces. Garnish with freshly chopped cilantro, if desired.