Combine 1/2 cup of water, salt, sugar, peppercorns, coriander and chiles over high heat in a medium saucepan. Bring to a boil and remove from heat. Add 1 1/2 cups of water and vinegar, stir to combine; let cool completely.
Scrub cucumbers to remove any dirt. Remove any tails or pieces of stem and cut in half lengthwise. (If you prefer them whole, that’s fine, just expect them to take an additional 3-4 days to fully ferment.) Divide cucumbers, garlic and dill sprigs among jars, making sure to pack the cucumbers tightly. Halve any remaining cucumbers crosswise to fill in the gap at the top.
Divide brine among jars, making sure to evenly distribute spices, leaving 1/4″ gap at the top of the jar.
Cover jars with cheesecloth and secure it with a rubber band. (This allows good bacteria to enter and keeps out dust and other impurities.)
Store in a cool, dark place (a cupboard or kitchen cabinet works great), and try not to disturb. Check pickles after 2 days to see how they are coming along (how fast they ferment will depend on their size). At this stage, you should have what is called a “half-sour”. Let them sit for an additional 2 days for a “full-sour.”
Place lid firmly on jar and refrigerate, these do not need to be processed again for canning. Store and enjoy for up to 2 months.
2 16-oz. Mason jars