Drain the oil from the canned tuna and set aside.
Wash the green onions thoroughly and slice them thinly.
In a bowl, mix the tuna, green onions, mayonnaise, salt, and pepper until well combined.
Spread the tuna and green onion mixture evenly on a slice of bread.
Cover with another slice of bread to complete the sandwich.
Cut into bite-sized pieces and arrange on a plate.