Last year I filled multiple delivery food containers with blackberries and strawberries from the garden, and blackberries from the massive plants that are along the road past the house. Some have been used for blackberry and apple (Bramley) crumble, and the rest got turned into jam today.
Simple 1:1 ratio of jam sugar to fruit, follow the instructions, boil, place into jars that had been washed clean, put on the lids and wait for the lids to stop flexing. Very tasty, and I can probably try again this year with 2:1 fruit to sugar.