Heat oven to 400˚. Using a 2″ round cookie cutter, cut out 24 circles from bread slices. Brush both sides of each circle with butter and transfer to a baking sheet. Toast bread in oven, turning once, until light golden, about 10 minutes.
Meanwhile, combine ham, mayonnaise, relish, salt and pepper to taste, and mustard in a small bowl. Spread about 1 tbsp. ham spread on each toast circle and top each with half an olive.