Wash the blueberries and remove any small stems.
Place in a bowl and either mash the blueberries with a potato masher, or do what I do and use an immersion blender. I like my blueberry jam pretty well blended, but feel free to leave some chunks of blueberries.
Transfer mashed berries to a large pot and begin heating on medium-high heat.
As the blueberries heat up, add the remaining ingredients. First add the 1 cup of juice and the lemon zest and juice.
Bring the mixture to a boil, then add in the pectin, stirring well as you add each tablespoon.
Bring mixture back to a boil and then add in the sugar.
Stir the sugar in well and continue stirring the jam. At this point you need it to heat up until it’s a hard boil- meaning that it continues to boil even when you’re stirring constantly. This should take about 10 minutes.
Spoon a small amount of jam into a small bowl and stick it in the freezer for a minute or two. Continue stirring the jam often while you wait for this small sample to cool off- it’s an easy way to see if the jam has set. After a minute or two in the freezer, the jam should look more set-up- mine was a tad thicker than maple syrup. When the jam is finished cooking and cooled, it will be much thicker- this is just a way to test it to make sure it’s not super runny. If your jam doesn’t appear to be setting up well, add in another 2 tsp of pectin and cook another 5 minutes, then test it again.
Ladle the hot jam into jars and process jars as you’d like- either by doing the inversion method, water bath canning, or you can even freeze or just put the jars of jam in the fridge. (They’ll last several months in the fridge.)
I water-bath canned mine. It’s not a complicated process but it does require a small investment to get the proper equipment.