My aunt lives near Paradise, MT has a beautiful guarding and makes some of the best home made things, including Blackberry Jam. She gave me the super simple recipe, one of the few recipes that isn’t a family secret and it comes right off the box. All you need to do is find a box of powder (not the liquid) Sure-Jell and follow the freezer jam directions. It is a favorite in our household and even better since we’ve grown the berries to make it!
I hope you and your family enjoy!