Chop, mash or puree strawberries and stir in the sugar. Let sit for 2 hours.
Add strawberry mixture to a large pot and cook slow over medium heat until it boils, stirring often. Then turn up the heat to med-high and boil fast for 5 more minutes or until candy thermometer says 220 degrees F.
Add in lemon juice and stir. Boil 5 minutes longer.
Pour jam into clean jars and add lids. Place in a hot water bath canner and boil for 10 minutes. Remove from water and let cool to room temperature. Store in a cool dry place for up to 1 year.
Jars that don't seal correctly can be placed in the fridge to be eaten within the next couple of weeks. Makes about 10 half pint jars of jam.