Wash the canning jars, lids, and bands in hot, soapy water. Rinse thoroughly. 

Place the jars in a large pot filled with water, ensuring they are fully submerged. 

Bring the water to a boil and let the jars boil for 10 minutes to sterilize them. Keep the lids and bands in simmering water until ready to use.

Place strawberries in a large stock pot, add sugar, and fresh lemon juice

Mash the berries (if they are too hard, wait to mash them)

Bring mixture to a full rolling boil over high heat and every so often mash the berries with a potato masher.

Once it’s boiling and you’ve mashed the berries, turn the down to medium high and add the corn starch slurry (corn starch plus water).

It will begin to thicken quickly, so do not take your eye off it.

Let cook for 5-6 min continuing to stir every minute or so.

Pour into a large bowl and let cool for 30-45 min at room temperature

Using a funnel, carefully ladle the strawberry preserves into the sterilized jars, leaving about ¼ inch of headspace at the top. 

With a clean, damp cloth or paper towel, wipe the rims of the jars to remove any residue or stickiness. 

Remove the lids from the simmering water and place them on top of the filled jars. Screw the bands onto the jars.

Place the filled jars into back into the water bath. Ensure that the jars are fully submerged in water, with at least 1 inch headspace of water covering the tops. Bring the water to a gentle boil and process the jars for 15 minutes.

Carefully remove the processed jars from the boiling water and place them on a clean towel or cooling rack. Allow the jelly jars to cool undisturbed for 12-24 hours.

Once the jars have cooled, check the seals by pressing down on the center of the lid. If the lid is firm and doesn't flex, the jar is sealed properly. Any unsealed jars should be refrigerated and used promptly.