Rinse your berries in a colander and set aside to drain and air dry a bit.
Line a rimmed baking sheet with parchment or a silpat.
Add the raspberries to the baking sheet and place the tray in the freezer. Pro tip: If you have a lot to freeze at once, lay another piece of parchment on top of the berries and top with an additional layer of fruit.
Freeze for 2 hours.
Break apart any clumps that have formed on the baking sheet and transfer the blackberries to freezer-proof storage.