1. With a serrated knife, horizontally slice 1 inch off the top of the loaf. Pull soft center from bottom half of loaf, making a shell with 1/2-inch-thick walls. Reserve soft bread for other uses.
2. In a bowl, mix vinaigrette dressing, cucumber, tomato, and chives. Brush or spoon about half the dressing evenly over interior of the hollowed shell. Also spoon enough dressing on cut side of loaf top to moisten.
3. Layer cheese, bell pepper, turkey, salami, and onion in shell. Drizzle remaining dressing over filling. Set bread top over filling. Wrap sandwich in foil or plastic wrap and refrigerate at least 3 hours or up to 1 day.
4. Unwrap; cut into equal portions.