Crush blueberries in a large pot, and stir in lemon juice, sliced lemons, and pectin.

Heat over medium to high heat, stirring occasionally, until mixture comes to a boil.

Add sugar, all at once, and stir until dissolved.

Bring back to a full, rolling boil and boil for one minute.

Remove from heat, and skim foam.

Ladle hot jam into sterile jars, wipe rims clean, and screw down bands and lids.

Gently place jars in a hot water bath canner, making sure the water level is at least one inch deep over the tops of the jars.

Place the lid on the canner, and bring to a full, rolling boil.

Boil half pints for 15 minutes, or pints for 20 minutes.

Remove from heat and let cool for at least an hour.

Check for seal after 24 hours, wash jars if needed, and store in a cool place out of direct light.