For topping:chopped nuts, toasted coconut flakes, cocoa powder, chocolate sprinkles
Place the raisins in a small bowl and pour very hot water over the top to cover. Let sit 5 minutes, then drain and lightly pat dry.
Place the nuts, oats, and flaxseed in the bowl of a food processor fitted with a steel blade, then blend until finely ground. Add the drained raisins, honey, vanilla extract, and salt. Pulse until a thick, sticky ball forms.
Remove the ball from the food processor, then roll into individual small balls, about 1 inch across. Sprinkle any desired toppings on individual plates, then roll the balls in the toppings to coat. Place balls on a parchment-lined baking sheet and freeze until no longer sticky. Transfer to an airtight container and store in the refrigerator or freezer.