Preheat your oven to 375°F (190°C).

Lay the flank steak on a cutting board and slice it horizontally to create a pocket.

In a mixing bowl, combine chopped spinach, ricotta cheese, shredded mozzarella, sun-dried tomatoes, minced garlic, dried oregano, salt, and black pepper.

Spoon the filling into the flank steak pocket, spreading it evenly.

Roll the flank steak tightly and secure it with kitchen twine.

In an oven-safe skillet, heat olive oil and sear the stuffed flank steak for 4-5 minutes on each side.

Transfer the skillet to the preheated oven and bake for 20-25 minutes.

Let the stuffed flank steak rest for 10 minutes, then slice into 1-inch rounds.