Weighting the garlic bread while it cooks makes itdenser and crisp.
Puree garlic and oil in a blender. Brush cut sides of bread with garlic oil; season with salt and pepper. (Refrigerate remaining garlic oil in an airtight container up to 1 month.)
Heat an 8-inch cast-iron skillet over medium heat. Lay bread, cut side down, in skillet. Place a lid small enough to fit inside skillet over the bread, and cook, gently pressing down on the lid and flipping bread once, until golden brown, 3 to 4 minutes per side.