Slice bananas into 18 "coins" each and lay them on a baking sheet covered in freezer paper or silicone baking mats.
Place nut or seed butter in a sandwich bag, cut a small corner off, and pipe a½ teaspoon nut or seed butter on top of each banana slice. If necessary, use your fingers to smooth the nut or seed butter.
In a glass bowl, melt chocolate and coconut oil together by microwaving in thirty second increments and stirring in between.
To dip the peanut butter banana bite in chocolate, place the banana flat on the tongs of a fork (nut butter side up). Dip in chocolate, using a spoon to help drizzle the chocolate on top of the banana bite. Shake off excess chocolate by hovering the fork over the bowl of melted chocolate, then gently tap the wrist of the hand holding the fork to help excess chocolate drip off. Run a toothpick under the tongs of the fork to eliminate any pooling chocolate, then transfer chocolate-covered banana bite back to the silicone baking mat.
If desired, garnish with flaky sea salt, peanut butter powder, slivered almonds, or a pumpkin or sunflower seed.
Freeze for four hours or longer.
Can be stored in a freezer-safe airtight container up to one month.