Line a small baking sheet or plate with parchment paper.
Peel 1 banana; place on the prepared parchment.
Top with another piece of parchment paper.
Press with another small baking sheet or a heavy skillet until flattened.
Place chocolate pieces in a microwave-safe bowl.
Microwave on High, stirring every 30 seconds, until melted, about 1½ minutes.
Spread the melted chocolate evenly over the banana.
Sprinkle with a pinch of flaky sea salt.
Freeze until solid, about 1 hour.
Break into pieces to serve (or transfer pieces to an airtight container and store in the freezer for up to 1 month).
