Preheat your oven to 350°F (175°C).

Lay the flank steak flat on a cutting board. Using a meat mallet or a rolling pin, gently pound the steak to flatten it to about 1/4 inch thickness.

In a small bowl, mix together the minced garlic, parsley, oregano, cumin, paprika, salt, and pepper. Rub this seasoning mixture evenly over the flattened steak, ensuring it covers both sides.

Arrange the sliced hard-boiled eggs, cooked spinach, carrot slices, and roasted bell pepper strips over the seasoned steak, leaving a small border around the edges.

Carefully roll up the steak, starting from one of the longer sides, keeping the filling ingredients inside. Use kitchen twine to tie the roll securely every inch or so.

Place the rolled-up steak on a baking sheet or in a baking dish. Bake it in the preheated oven for about 1 hour, or until the steak is cooked through and tender.

Once cooked, remove the Matambre arrollado from the oven and let it rest for a few minutes. Remove the kitchen twine, and slice it into rounds.

Serve the Matambre arrollado warm or chilled, as an appetizer or a main course. You can accompany it with a side salad or some crusty bread.