Hull and chop the strawberries into small pieces.
Add strawberries, sugar, and lemon juice to a medium or large saucepan.
Cook over medium heat until the sugar has dissolved and the berries are juicy.
Increase the heat and bring the mixture to a rolling boil.
Cook until thickened and the mixture reaches about 220°F (105°C), stirring often.
If you don't have a thermometer, test a small spoonful on a chilled plate. The jam should hold its shape rather than run like syrup.
Remove from the heat and carefully transfer to clean jars.
Cool, cover, and refrigerate. The jam will thicken further as it chills.