Crush the blackberries and measure 3 cups into a large bowl.

Stir in the sugar and let it sit for 10 minutes.

Combine water and pectin in a small saucepan.

Bring the water and pectin mixture to a full rolling boil over high heat, stirring constantly, for 1 minute.

Stir the pectin mixture into the blackberry mixture and stir constantly for 3 minutes.

Fill plastic or glass freezer containers, leaving 1/2-inch space at the top.

Cover with lids and let stand at room temperature for 24 hours.

Store in the freezer.

After opening, store in the refrigerator for up to 3 weeks.