Unzip both ends of the insulated cylinder and lay it flat with the flap facing up.

Set the heat mat on the center of the flap inside the cylinder.

Zip both sides of the cylinder closed, positioning the power cord to exit through the gap between the two zippers.

Place your sourdough starter jar directly on the center of the heat mat.

Fold down the top flap of the cylinder to enclose the jar and retain warmth.

Plug the mat into a wall outlet and use the controller to set the temperature in 1°F increments.