Preheat oven to 200C.
Season spinach with salt and pepper.
Butterfly the steak and pound it to about 1/4 inch thick.
Season with salt, pepper, onion powder, garlic powder, and parsley flakes.
Layer with spinach and feta leaving about 1/2 inch border clear.
Then layer with mashed potatoes.
Roll it up..
Here you can secure the flank steak with kitchen twine 1 inch apart.
Season with more salt and pepper and lay it on an greased baking pan.
Bake at 200C for 25 mins.
Brush on BBQ sauce and bake for another 5 minute.
Then allow to rest for 10 mins for the juices to redistribute before cutting into it.
Serve with a side dish.