Boil salted water in a large pot
Add spaghetti and cook until al dente
Reserve some pasta water
Heat olive oil in a pan over low heat
Add sliced garlic and cook until fragrant and lightly golden
Add red chili flakes
Add cooked pasta to the pan
Toss with the garlic oil
Add reserved pasta water as needed
Add chopped parsley
Season with salt and black pepper
Serve immediately