Cut off the blossom end of the cucumber (about ¼ inch piece). This removes the enzyme that’s in the blossom that can tend to make pickles mushy. If you have any cucumbers that have soft spots or blemishes, set those aside for fresh eating and save the firm and blemish-free cucumbers for pickling.
Mix together 1 quart of warm water and ¾ cup of salt into a large two-gallon vessel. Stir well until the salt is dissolved, then add enough cold water to fill the vessel up to the two-gallon mark.
Place your prepared cucumbers into a 5-gallon food-grade bucket, pour in the brine, and submerge the cucumbers under the brine with a plate or weight. Allow cucumbers to sit in the brine, in the refrigerator, anywhere from 12 hours up to 7 days, but for the crispest pickles, move on to the next step within 3 days.
Tie your pickling spices in a piece of cheesecloth, butter muslin, or a loose-leaf tea bag. Add the pickling spices, 8 cups of water (filtered or distilled), 6 cups of 5% vinegar, ¼ cup sugar, and ½ cup salt to a large stockpot. Bring the brine up to a boil on the stovetop.
Meanwhile, get your canning pot ready and the water heating up to 140°F. Prepare your canning jars by washing them in hot, soapy water and rinsing them well. Then, while still warm, place them on a kitchen towel on the counter.
Fill each canning jar with one clove of garlic, one teaspoon of mustard seed, and one teaspoon of dill seed. Slice your cucumbers into spears (or leave them whole, or slice them into coins) and pack your jars as full as possible.
Once your brine has come up to a boil, remove it from the heat and immediately fill your jars with brine, leaving ½ inch headspace. Using a bubble remover, slide it down around the edges of the jar to allow any bubbles to escape. If needed, adjust headspace by adding more brine. Add your two-part canning lids and tighten to fingertip tight.
Transfer your jars to your water bath or electric canner and adjust the water level, if needed, so the jars are covered with 1-2 inches of water. Using your thermometer, bring the water temperature up to 180°F. Once your water is up to temperature, set your timer and keep the water temperature between 180°F-185°F for a full 30 minutes. If you’re using a stovetop, this can be a bit tricky, and if the temperature drops below 180°F, you need to start your time all over again. This is why I really prefer using my electric canner for this method.
Once 30 minutes have passed, carefully remove the jars from the canner using a jar lifter and set them on a towel-lined counter. Let your jars sit for a full 12 hours (or overnight) before checking the seals, labeling the jars, and moving them to the pantry. Any jars that did not seal correctly can be moved to the refrigerator and enjoyed immediately.