Wash the jars, lids, bands, and canning tools in warm, soapy water.

Place the water bath canner on the stove. Place the jar rack into the pot, set the jars in the canner, and fill with enough water to cover the jars.

Bring the canner to a simmer (180˚F) for 10 minutes, and keep the jars warm until you are ready to fill them.

Rinse the tomatoes well under clean running water, remove the cores, then cut them into 1/2-inch slices, discarding the ends.

To make filling the jars easier, dry fit the sliced green tomatoes into an extra jar, leaving just under a 1/2-inch headspace. Then, empty the jar upside down on a plate so you have a stack ready to fill a warmed jar. Continue this process with the remaining slices.

Fill a large pot with water, set it on the stove, and bring it to a boil. This is the water you will use to fill your jars.

Spread a kitchen towel on the counter. Use the jar lifter to remove ONE jar from the canner. Drain the water back into the canner and place it on the towel. Keep the remaining jars in the canner so they stay warm.

Run the bubble popper around the jar to release any air bubbles, and adjust the headspace if needed with additional boiling water.

Wipe the rim with a clean, damp towel. Add the lid and secure it with a screw band until it's fingertip tight. Return the jar to the canner. Then, repeat with the rest of the jars.

Once the filled jars are all in the canner, adjust the water level so it is at least 2 inches above the tops of the jars.

When the processing time is complete, turn off the heat, remove the lid, and let the canner cool and settle for about 5 minutes.

Spread a dry kitchen towel on the counter. Then, use the jar lifter to remove the hot jars from the canner and place them on the towel. Keep the jars upright, and don't tighten bands or check the seals yet. Let the jars sit undisturbed for 12 to 24 hours to cool.