Butterfly the flank steak by slicing it horizontally through the middle, stopping about an inch from the other side, then open it like a book.
Pound the steak evenly with a meat mallet to ensure it cooks uniformly.
Apply a thin layer of avocado oil over the steak.
Season the steak with salt, pepper, and garlic powder or an all-purpose rub.
Lay 6-8 slices of provolone cheese over the steak.
Add 4-6 slices of prosciutto on top of the provolone.
Sprinkle shredded mozzarella cheese over the prosciutto.
Spread baby spinach leaves evenly over the cheese and prosciutto.
Drizzle a bit more avocado oil over the spinach and season with additional salt and pepper.
Carefully roll the steak with the grain going left and right, then tie with butcher's twine, spacing the ties about 1 to 1 1/4 inches apart.
Slice the rolled steak into pinwheels and insert a bamboo wood skewer through each pinwheel to hold them in place.
Preheat a griddle to medium temperature (425-450°F).
Add avocado oil to the griddle and cook the pinwheels for 2-3 minutes on one side, then flip and cook for an additional 2-3 minutes. If needed, move to indirect heat to finish cooking.
Serve the pinwheels hot and enjoy!