Crush the strawberries with a potato masher, or by blending briefly in a food processor using the pulse setting so that there are pieces of strawberry rather than a fine purée. Add to a large bowl and stir in the sugar, then cover and leave to stand for 1½–2 hours, stirring from time to time, until the sugar has dissolved.
Stir in the lemon juice, then add the pectin and continue stirring for 2 minutes. Ladle into small clear plastic pots leaving a gap of 1 cm (½ inch) at the top. Clip or press on lids. Label and leave at room temperature overnight for the conserve to 'gel'.
Transfer to the freezer to store until required. Defrost overnight in the refrigerator, then transfer to attractive jars and serve in the same way as a conventional jam.