Wash, hull and cut strawberries in half.

Working in batches, place in a single layer and roughly mash with potato masher (I find a glass 13" x 9" baling dish works well for this). Continue until there is a total of 5 cups mashed.

Place mashed berries, lemon juice and sugar in a large pot over medium high heat. Stir.

Bring to a rolling boil.

Adjust heat as needed to keep at a rolling boil for twenty minutes. Stirring often and checking to make sure nothing sticks to the bottom or sides of the pot. Fruit should cook down and liquid thicken (looking less like fruit and liquid are separate or floating).

Remove from heat and pour into a glass bowl or large (8 cup) measuring cup.

Using a metal spoon, carefully scoop the foam from the surface.

Ladle or pour into sterilized canning jars. Fill until 1/4" from the top. Place a new clean sealing lid on top and loosely thread rim into place. Repeat with remaining jam and jars.

Place into canner and make sure the water covers the lids by 2 inches.

Bring canner to a boil. Boil for 10 minutes.

Carefully remove jam with canning tongs to a towel on the countertop. Allow to rest undisturbed for 24 hours.