Carefully cut off the top portion of the salt carton.
Use the canning lid as a template and draw a circle on the top of the piece you cut off the carton. Center it over the metal spout.
Ready to cut out.
Carefully cut out your circles. You will need sharp scissors for this, the cardboard is stiff, and being on a curve it is hard to cut through.
That's it! Place cut piece on the jar and screw on canning ring to seal.