Here’s the way to do it.
Slice the green tomatoes as you would for fried green tomatoes.
Put the slices in a wide mouth canning jar.
Try am pick ones that fit the jar, the diameter.
Put into each jar a teaspoon of salt and a TBLS. lemon juice.
Fill the jars with hot water to 1/2 ‘” from the top, run a butter knife around the outside of the tomatoes to release any air trapped.
Put jar rings on and put them into a boiling water bath for about 40 minutes.