Hull and quarter the strawberries and place them in a large 8 quart, heavy bottomed saucepan.
Crush the strawberries with a potato masher leaving some lumps of strawberries for texture. Stir in the lemon juice and pectin.
Place the saucepan over high heat and bring the strawberries to a full rolling boil.
Add the sugar, stirring to dissolve, and bring the mixture back to a boil.
Lower the heat to medium and allow to actively simmer for about 20 minutes, stirring frequently to keep sugar from scorching.
As the jam is simmering, use a metal spoon to remove the scum that rises to the surface of the jam.
When you see the jam has thickened and the fruit is almost translucent, turn off the heat and test the set by adding a dollop onto the cold plate. Place back in the fridge for 10 minutes to chill. If the jam wrinkles when touched then your jam is ready. If it is loose and has spread then place the saucepan back on the stove to cook for longer.
Canning the jam: Place a steamer tray or rack in the bottom of a large saucepan. Fill the pot ¾ of the way with water. Place on high heat and bring to a simmer.
Wash 4 (8 oz) jam jars and lids in hot soapy water before drying well.
While the jars are still warm, fill them up to a ¼ -inch (6mm) from the top with the hot jam.
Rub the rim with vinegar or hot water. Place the canning lids on and turn the lid to ‘fingertip tight’. Turning too tight and your seal can buckle.
Using tongs, carefully lower the jam jars in the saucepan making sure the water covers at least an inch over the top of the jar.
Place on a lid and simmer for 10 minutes to process the jar. Make sure to do the full 10 minutes as this time also is to sterilize the jars.
Carefully remove the jar from the pot and set aside to sit at room temperature for around 12 hours to cool completely.
When cool, check for a proper seal: If it is flat and it doesn’t bounce back when pushed then it is good to be stored in the cupboard for up to 1 year. If it does bounce back, store in the fridge and use within 4 weeks.