Wash cucumbers thoroughly and trim both ends.

Slice cucumbers into 1/4-inch rounds using a mandoline or sharp knife.

In a large container, dissolve 6 tablespoons salt into 1 gallon of water to make the brine.

Add sliced cucumbers, cover, and let sit for 8 hours. Drain completely.

Prepare the pickling solution by bringing 1 quart vinegar, 1/4 cup salt, and 1 quart water to a boil.

Sterilize jars and keep them hot.

Into each hot jar, add 1 teaspoon mustard seed, 1–2 dill heads (or 1 tsp dried dill), 1 peeled garlic clove, and 1/2 teaspoon black peppercorns.

Pack jars tightly with cucumber slices, leaving 1/2 inch of headspace.

Pour hot pickling solution over cucumbers, maintaining 1/2 inch headspace.

Remove air bubbles using a rubber spatula or wooden utensil.

Wipe jar rims with a clean, damp cloth.

Seal jars with clean lids and rings, fingertip-tight.

Process jars in a boiling water canner: 10 minutes for pints, 15 for quarts. Adjust for altitude.

Let cool. Check seals. Store sealed jars in a cool, dark place. Wait 1–2 weeks before opening for best flavor.