I always recommend peeling the banana before you freeze it because trying to peel a frozen or thawed banana is a certified nightmare!
You might also consider cutting the banana into pieces because most recipes that call for frozen bananas usually require it to be chopped up
Sprinkle, spray, or brush the banana with some fruit juice (lemon, orange, or lime) in order to stop them from turning brown. The acidity of the fruit juice slows down any oxidation
If you’ve kept the banana intact rather than cutting it into pieces, wrap the banana in plastic wrap to add a layer of protection
If you’ve cut the banana into pieces then lay them out of a baking tray and flash freeze them. To flash freeze, place the banana in the freezer for 2-3 hours.
After 2-3 hours the banana will be mostly frozen and you can transfer the pieces to a Ziploc bag or airtight container. Flash freezing ensures that the pieces will not stick together. This makes it easier to pick out however many pieces you need whenever you need them