Preheat oven to 450º F. Get a deeper sheet pan ready. Also preheat the pan to medium high heat. You will be cooking the chicken in a pan first to get the skin nice and crispy.
Pat the chicken dry completely with a paper towel on both sides. Using 1 tbsp of sea salt sprinkle both sides and rub it in well. Once your pan is heated up. Add 1 tbsp of olive oil. Gently add the chicken away from you skin side down. Cook for 7-8 minutes or until skin is golden brown and feels crispy to touch. Flip over and cook for 2 more minutes.
While chicken is cooking prep your veggies. Peel and clean the onions. Cut them in half and then in half again, slice into 1/4 inch half circles. Wash your potatoes, cut in half and then cut in 1/4 inch thick slices. Salt with remaining 1 tbsp of sea salt.
FOR THE GARLIC SAUCE: You have the option to either make a batch of garlic sauce called TOUM, find the recipe here. Buy some at Trader Joes, it's called Garlic Dip or use 6 cloves of garlic, grate very finely and toss with a few tbsp of olive oil to make a sauce. This will be the sauce to toss for the potatoes and onions in.
Add the garlic tossed onions and potatoes in a oven safe dish. Sprinkle with dried oregano. Toss well. Add the crispy skinned chicken, skin side up. Scatter the tomatoes, olives, pepperoncini and feta. Don't add anything on top of the chicken.
Bake UNCOVERED for 30 minutes on the top rack, rotate half way to ensure all the chicken gets even more crispy and the veggies cook evenly.
Once baked, remove from the oven, sprinkle with fresh parsley and enjoy! Can be served on it's own or with a side or greek style salad.