01 - Preheat oven to 400°F. Lightly grease a baking dish with olive oil.
02 - Heat 1 tablespoon olive oil in a skillet over medium heat. Sauté minced garlic for 30 seconds, then add chopped spinach. Cook until wilted, approximately 2 minutes. Remove from heat and allow to cool slightly.
03 - In a mixing bowl, blend the cooled spinach mixture with crumbled feta, cream cheese, dried oregano, and red pepper flakes until thoroughly combined.
04 - Pat chicken breasts dry with paper towels. Using a sharp knife, create a horizontal pocket in each breast without slicing through completely.
05 - Season the exterior and interior of each chicken breast evenly with salt and black pepper.
06 - Fill each pocket with the spinach and feta mixture. Secure openings with toothpicks if necessary.
07 - Place stuffed breasts into the prepared baking dish and drizzle with remaining tablespoon of olive oil.
08 - Bake in the preheated oven for 25 to 30 minutes, or until the internal temperature reaches 165°F and juices run clear.
09 - Remove toothpicks before serving. Let the breasts rest for 5 minutes, then slice and serve.