Prepare the Ingredients. Wash and slice the cucumber, tomato, and red onion. Peel and slice the avocado. Wash and dry the lettuce or spinach.
Assemble the Sandwich. Spread a generous layer of hummus on one side of each slice of bread. Layer the cucumber, tomato, red onion, avocado, and lettuce or spinach on one slice of bread.
Combine and Serve. Place the other slice of bread on top to form a sandwich. Cut in half if desired. Serve immediately.