There are two main methods for freezing bananas: one is to place them on a cookie sheet lined with parchment paper and freeze them for at least two hours. From there, you can transfer the slices to a bag or container. If you prefer, you can use a banana freezing tray, which is more efficient at freezing the fruit. But beware of overfreezing your bananas as the water in the fruit can freeze to sharp ice crystals, which will puncture the cell walls, making the bananas less firm.