Preheat your oven to 425°F (220°C).
Place a 10- to 12-inch cast iron skillet on the stovetop over medium heat. Add olive oil to the skillet and swirl to coat the bottom.
Add green beans to the skillet and toss them gently to coat in the oil. Let them cook undisturbed for 2 minutes so they start to brown on one side.
Sprinkle in kosher salt and freshly ground black pepper. Stir the green beans and cook for another 2 to 3 minutes, stirring occasionally, until they begin to blister and char slightly.
Add minced garlic and stir to combine. Cook for 30 seconds until fragrant.
Transfer the skillet to the preheated oven and roast for 10 to 12 minutes, stirring once halfway through, until the green beans are tender with crispy edges.
Serve warm.