Preheat oven to 400°. Put peppers in a large baking pan and bake until soft when pressed, 40 to 50 minutes. Let cool 10 to 20 minutes to loosen skin.
Meanwhile, with a mortar and pestle, mash garlic with salt into a paste (or mash garlic with salt with the flat side of a chef's knife, then put into a small bowl). Stir in olive oil to blend.
Peel, stem, and seed peppers and cut lengthwise into 3/4-inch-wide strips. Arrange peppers on a platter and drizzle with garlic oil, scraping it out of the mortar or bowl to get all the garlic. Serve warm or at room temperature.