This technique is as simple as it sounds. Here, chicken is weighed down by a brick (or otherwise heavy object like a cast iron pan or plate with soup cans placed on top) while it cooks in a pan or on the grill.
Under pressure, the chicken skin gets crackly and infused with whatever herbs and seasonings that are cooked with it. If you do use an actual brick, we recommend wrapping it in tin foil first. Check out the video from Food52.
Try this recipe for Herb & Citrus Chicken Under a Brick.