In a large heavy-bottomed kettle, combine the strawberries, sugar, and lemon juice. Bring to a rolling boil on the stove. Remove from the heat and strain the liquid from the strawberries. Return the liquid to the heat and gently boil until the liquid reaches 221°F. Add in reserved strawberries and continue to boil for 5 minutes.
Prepare boiling water in a large pot for canning.
Remove the foam from the strawberries, if desired. Remove from heat and mash or blend strawberries to desired consistency.
Pour in sterilized jars leaving ¼-inch headspace. Wipe off the rim of the jar with hot water.
Prepare lids to the manufacturer's instructions on the package and place them on each jar with a ring, turned finger tight.
Boil in a water bath for 10 minutes, making sure to adjust for your location's altitude.
Remove from the water bath and cool at room temperature for 24 hours. Make sure the jars are sealed. When you press down on the center, there should be no flex.