Slice strawberries so all pieces are approximately the same size. For some strawberries, this will mean cutting in half, and for other larger berries they may need to be quartered.
Place strawberries, sugar, lemon juice, and lemon zest in a medium sauce pan, then bring to a rapid boil over medium heat.
Stir occasionally with a spatula, helping to break up and mash the strawberries as you go. Check consistency of preserves.
Dip a spoon into the sauce pan, then pull it out and run your finger along the back.
Remove preserves from the heat and pour into glass jars. Wipe the rim, cover and seal, then allow to cool completely before storing in refrigerator until needed.