I freeze blackberries every year.
You can lay them out individually on a cookie sheet, place in the freezer and when they are frozen, bag them in amounts suitable to what your family likes. This is excellent for making jam or pies.
You can also rinse them, add sugar to taste, pack in containers sized for your family and let them stay in the refrigerator for a day or two before freezing. If you just like to eat them plain, I prefer this method. They will be juicier than the dry frozen method.
Mine are the wild ones. Hybrids and those bought from the store are larger, with more juice to begin with.
Thank you for the information. I am going to try both ways.