Lightly toast or grill the bread slices. If using a grill pan you can brush with olive oil.
Cut the grilled bread into heart shapes using a sandwich cutter: Line up the sandwich cutter in the center of a slice of bread. Press down firmly, until it cuts through completely, leaving you with a heart-shaped piece of bread.
Spread one slice of the prepared bread with 3 tablespoons of the hummus. Layer on top half of the lettuce, carrots and avocado. Repeat with the remaining ingredients.