Combine chili powder, cumin, granulated garlic and salt in a small bowl.
Pre-heat the oil over medium low heat in a pot large enough to hold the chicken in a single layer. A dutch oven would work here.
Add the spice mixture and stir constantly for about 20-30 seconds. Be careful not to burn the spices. Have the chicken stock at hand in case it looks like it's getting away from you. You can stop it with a splash of stock.
Add 1/4 cup of chicken stock and stir.
Add the chicken to the pot along with enough stock to come up about 2/3 of the way up the chicken.
Cover and simmer for 15 minutes.
After the first 15 minutes, uncover and flip the chicken thighs. Continue to cook for about another 15 minutes.
Remove chicken from the pot and skim off as much fat as you can from the remaining liquid. Turn the heat up to medium and reduce the liquid until you get to about 1/2 cup.
Let the chicken cool until it's comfortable to handle. Remove the chicken from the bone and shred coarsely. Your hands work best here.
Spoon the reduced liquid over the shredded chicken. You don't have to use all of. Do what tastes good to you.