Prep the green beans by washing them thoroughly under cold water. Trim the stem ends and pat the beans completely dry with paper towels or a clean kitchen towel—this is crucial for achieving crispiness.
Preheat your air fryer to 375°F (190°C) for 3 minutes. Proper preheating ensures even cooking and better texture.
Season the green beans by placing them in a medium bowl and drizzling with olive oil. Add salt, pepper, and minced garlic (if using), then toss until all beans are evenly coated.
Arrange the beans in a single layer in your air fryer basket. Avoid overcrowding—work in batches if necessary, as overcrowding will steam rather than air fry the beans.
Cook for 5 minutes, then shake the basket or use tongs to flip the beans. This ensures even cooking on all sides.
Continue cooking for 4-5 more minutes until the beans are bright green with some golden-brown spots. They should be tender-crisp, not soft or mushy.
Taste and adjust seasoning if needed. If using, sprinkle with red pepper flakes, fresh lemon juice, or Parmesan cheese while still hot.
Serve immediately for the best texture and flavor experience.