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Dust the marshmallows with more rice flour before serving them.
Fill a rimmed baking sheet with more sweet rice flour. Roll the marshmallow cubes in the flour until they are coated; this will keep them from getting sticky. Dust off the excess flour, then store them in a sealed container in the fridge. They will last up to 1 week. You can use cornstarch and/or powdered sugar for this step.