Bring salted pasta water to boil. Cook pasta.
In a skillet, heat olive oil. Add chopped garlic cloves and saute until golden brown.
Add canned, crushed tomatoes and cook for a few minutes, then add chili flakes, dried basil, salt, and pepper. Season to taste.
Add fresh basil and simmer about 5 minutes. Finally, add spinach and cook until it wilts. Simmer for another 5 minutes.
Add drained pasta to sauce, reserving about 3 tbsp of the pasta water and adding it all into the sauce.
Stir until pasta is fully mixed in with the arrabbiata sauce. Garnish with more chili flakes, fresh basil, and flaky sea salt.