Heat oil in a large pot over medium heat until oil is shimmering. Cook garlic in oil for no more than 30 seconds. Add all of the chicken to the pot; cook, stirring frequently, until chicken is white all over. Do not brown.
Pour in soy sauce, vinegar, and water, and add the pickling spice. Make sure the spice ball is submerged. Bring to a boil, reduce heat to simmer, and place lid on pot so that some steam can escape. Simmer for 1 hour, or until chicken is very tender.