› recipes › fruit-recipesHomemade strawberry jam recipe | Jamie Oliver fruit recipes Either put them in the sink (lids unscrewed from jars) and cover them with boiling water from the kettle, filling the jars with the water; or simmer them, completely immersed, in a very large pan of boiling water for 10 minutes; or lay the jars and lids on a baking tray in the oven and heat them at around 100°C/225°F/gas ¼.