Pour the filtered water into a clean widemouthed quart-size jar. Pour the salt into the water, cover with a tight fitting lid and shake to dissolve the salt.

Add the mustard seeds, peppercorns, bay leaf, dill, and garlic, then add the green beans. Pack the beans in tightly, squeezing as many as possible into the jar, making sure the brine covers the vegetables. If it doesn’t cover the beans, mix a heaping 1½ teaspoons of salt with 1 cup of water, then pour in enough to cover the vegetables. Seal the jar.

Let the beans sit at room temperature for 5 to 7 days, briefly opening the jar once every couple of days to “burp” it (releasing carbon dioxide). You’ll notice that the beans will turn pale after about 2 days. The time the beans take to ferment fully will vary depending on air temperature and elevation. Taste the beans each day after the fifth day until the desired level of sourness is reached. The brine will begin to appear cloudy and may be a bit fizzy. That’s fine.

When you are happy with the taste of the beans, remove all white yeast or mold from the top of your jar, if any has appeared. Cover the jar and place the pickled beans directly in the refrigerator. They will keep for up to 6 months.