Peel and slice the bananas into 1/2-inch (1.25 cm) thick rounds. You should get about 10-12 slices each, depending on their size.
Line half of the banana slices on a plate or baking sheet covered with parchment paper. Spread a layer of peanut butter over each slice, then top with another banana disc to form a sandwich.
Freeze for at least 30 minutes.
Place dark chocolate chips in a microwave-safe bowl with 1 teaspoon of coconut oil. Microwave in 30-second intervals, stirring in between, until the chocolate has melted completely.
With the help of one or two forks, dip each peanut butter banana sandwich into the melted chocolate. Transfer the chocolate covered bites back to the plate or baking sheet, then sprinkle with flaky salt if desired.
Freeze for about 30 minutes, until the chocolate has hardened.
Serve, or keep in an airtight food container in the freezer for up to 2 months.