If your recipe says to process the jam - I have no idea if they do or not - you can use a pressure cooker like a hot water bath canner - just leave the gasket off/out of the lid and the pressure thingy off the lid (if that's how yours works)
and cover the jars with water to over one inch.
If that's what the instructions call for.
My Mom made freezer strawberry jam. Awesome. But it did have sugar in it.