Rinse the blackberries gently under cold water
Drain them well
Pat them dry with a clean towel or paper towels
Remove any stems, leaves, or damaged berries
Spread the blackberries in a single layer on a baking sheet
Place the baking sheet in the freezer until the berries are solid
Transfer the frozen blackberries to a freezer-safe bag or container
Remove as much air as possible before sealing
Label the container with the date
Store in the freezer until ready to use