Spread peanut butter on one side of each slice of bread. Peel the banana and cut into round slices about 1/2 inch thick. Place the banana slices on one of the peanut butter-covered slices of bread (you might not need quite the whole banana) then top with the remaining slice.
Notes
Even my 2-1/2-year-old can manage this himself – although he’s pretty messy about it – because it only requires a butter knife and the banana slices easily.