Preheat the oven to 400°.

Rinse and dry the trimmed Brussels sprouts.  If you have a salad spinner, this is the perfect time to use it!  Remove and reserve any loose outer leaves.  In a large mixing bowl, toss the Brussels sprouts with enough olive oil to coat and season generously with salt and pepper.  Place in a single layer on a large baking sheet.  Place the reserved loose leaves in the same mixing bowl and toss with a spoon to pick up any olive oil and seasoning remaining in the bowl.

Your total cooking time will be between 20 to 30 minutes, depending on how crisp/tender you prefer your sprouts.  Roast for 10 to 15 minutes, shaking the pan occasionally to move the sprouts around.  Remove from the oven and add the Brussels sprout leaves.  Continue to roast for 10 to 15 minutes longer, to your desired tenderness.  Remove from the oven and sprinkle with flaky sea salt before serving.