Preheat oven to 350 degrees F. Pat chicken thighs dry with a paper towel and season liberally with salt and pepper.
Heat olive oil in a large oven-safe skillet over MED-HIGH heat. Once oil is rippling, add the chicken thighs, skin side down and cook for 5 minutes, or until golden brown and seared.
Turn chicken over and cook on the other side for another 4-5 minutes.
Remove chicken to a plate to rest.
Add onion to the pan and saute for 1-2 minutes.
Add potatoes, smashed garlic cloves, olives, and minced oregano and stir to combine. Cook, stirring occasionally, for 4-5 minutes.
Sprinkle flour over vegetables and stir. Add wine and allow most of the liquid to cook off (just a few minutes).
Pour in chicken stock and stir. Nestle the chicken thighs into the pan and tuck the lemon slices in among the chicken and vegetables. Toss in the rosemary sprig.
Cover pan with lid (or foil), and bake for 40 minutes, until potatoes are tender and chicken is cooked through. Remove rosemary stem.
The remaining juices should have thickened into a makeshift gravy you can spoon over the top of the chicken when serving.
Garnish with lemon zest and additional oregano or fresh parsley if desired.