Make harissa: In a mortar with a pestle, an electric spice grinder, or a cleaned coffee grinder grind seeds fine. If using mortar and pestle, add chilies, garlic, and salt and pound to taste. If using a spice or coffee grinder, transfer seeds to a small food processor and add chilies, garlic, and salt. Grind mixture to a paste. Add pepper and oil and pound or purée to a coarse paste.

In a large bowl stir together harissa and olives and marinate, covered and chilled, at least 6 hours or overnight. Olives may be prepared 1 week ahead and kept chilled, covered.

Serve olives at room temperature.

To roast peppers:
Using a long-handled fork, char peppers over an open flame or on a rack set over an electric burner, turning, until skins are blackened, 4 to 6 minutes. (Or to broil peppers on rack of a broiler pan under a preheated broiler about 2 inches from heat, turning every 5 minutes, 15 to 20 minutes, or until skins are blistered and charred.) Transfer peppers to a bowl and let stand, covered, until cool enough to handle. Keeping peppers whole, peel them, starting at blossom end. Cut off pepper tops and discard seeds and ribs.

Makes about 3 cups.