In a bowl, stir together cream cheese, carrot, zucchini, sweet pepper, and chives. Add salt and cayenne to taste. Cover and chill for at least 1 hour or up to 24 hours.
Spread 4 slices of the bread with dairy sour cream. Arrange salmon on top of sour cream. Add spinach leaves. Spread 4 more slices of the bread with vegetable spread; set on top of sandwich bases, spread side up. Arrange cucumber slices on spread. Top each sandwich with another slice of bread. Cut sandwiches into quarters. Makes 8 side-dish servings.