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, about 2 minutes. Remove from heat and cool slightly.
03 - In a mixing bowl, blend the cooled spinach, crumbled feta, softened cream cheese, dried oregano, and red pepper flakes until fully incorporated.
04 - Pat chicken breasts dry. Using a sharp knife, create a horizontal pocket in each breast, taking care not to cut completely through.
05 - Season the interior and exterior of each chicken breast evenly with salt and black pepper.
06 - Fill each chicken breast pocket with the spinach and feta mixture. Secure openings with toothpicks if necessary.
07 - Place the stuffed chicken breasts in the prepared baking dish and drizzle with 1 tablespoon olive oil.
08 - Bake for 25 to 30 minutes, or until the internal temperature reaches 165°F and juices run clear.
09 - Remove toothpicks. Let chicken rest for 5 minutes before slicing and serving.