• 1/2 tsp. grated lemon zest plus 1 tbsp. fresh lemon juice
Dry chicken with paper towels and season with salt and pepper. Heat 1 tablespoon oil in 12-inch skillet over medium-high heat until just smoking. Add half of chicken, skin side down, and brown lightly, about 5 minutes; transfer to plate. Repeat with 1 tablespoon more oil and remaining chicken; transfer to plate. Let chicken cool slightly and discard skin.
Add onions, half of garlic, oregano and red pepper flakes to fat left in pan and cook over medium-high heat until onions are softened and lightly browned, 8 to 10 minutes. Stir in flour and cook for 1 minute. Slowly whisk in wine, scraping up any browned bits and smoothing out any lumps; transfer to slow cooker.
Microwave potatoes with remaining 1 tablespoon oil in covered bowl, stirring occasionally, until nearly tender, about 5 minutes; transfer to slow cooker. Stir broth into slow cooker. Nestle browned chicken with any accumulated juice into slow cooker. Cover and cook until chicken is tender, 4 to 6 hours on low.