If you aren't familiar with freezer jam, check out this great NPR article on it: Freezer Jam: A Baby Step to Canning
Blackberry Freezer Jam
4 cups of crushed blackberries (I used a potato masher. You can remove the seeds by using a sieve if you wish, but I left mine in)
1.5 cups of sugar ( do not use less/more or substitute another type of sweetener, it's what's needed to make it gel)
5 (8 oz.) containers (you can use freezer jars, (straight-sided) jelly jars, any sealable plastic containers)
1 package of Ball's Instant Fruit Pectin (1.59 oz.)
1. Stir sugar and pectin in a bowl.
2. Add crushed fruit and stir well.
3. Ladle jam into clean jars and let it stand for 30 minutes.
4. You either eat it then or freeze it.
5. Freezer jam can be frozen for up to 1 year. Once thawed, it must be kept in the fridge and it's good for up to 3 weeks.