Place an ovenproof skillet on the stovetop and add oil. Preheat to medium high.
In a large zipper-close bag or a bowl with a lid, put the sea salt, pepper and garlic powder and gently stir to mix.
Add the chicken to the bag or bowl, close and shake to cover the chicken with the seasoning mixture. By this point, the oil in the skillet should be hot.
Put chicken in the skillet and brown for 3-4 minutes per side.
Transfer the skillet to the oven and bake for 15-20 minutes, depending on the thickness of the chicken breasts.
Remove from the oven and let the chicken sit for 5 minutes before serving.