Mash the banana in a large bowl until mostly smooth. Add peanut butter, honey, and vanilla. Stir well until the mixture looks creamy and evenly combined.
Add the oats, walnuts, flaxseed, chocolate chips, cinnamon, and salt. Stir until everything comes together into a soft dough. If using quick oats, let the mixture sit for 5 minutes. If using rolled oats, place it in the fridge for about 20 minutes.
Scoop about 1 to 2 tablespoons of mixture. Roll into balls using slightly wet hands to prevent sticking.
Place the balls on a plate or tray. Chill in the fridge for 20 to 30 minutes, until firm and easy to hold.
