Using a mandoline or sharp knife, slice the cucumbers to approximately 1/4" thick.
In each pint-size jar, place 1 1/2 teaspoons of coarse ground sea salt in the bottom of each jar. If using, add 1/4 teaspoon of red pepper flakes to each jar.
Divide the cucumbers and the dill between the three jars, alternating layers of cucumbers and dill. Pack very tightly.
Place a pickle pebble or other weight on top of the cucumbers and fill each jar with water, leaving 1" headspace. Make sure that all the cucumbers are fully submerged under the water. Place a lid on each jar and tighten securely.
Place all three jars into bowls or on a tray to catch any liquid that might leak out during the fermentation process.
Place jars in a room-temperature area (68°F to 72°F or 20°C to 22°C) out of direct sunlight. Check the jars each day, loosen the lids to release any gasses that are building up, and then re-tighten the lids.
After three days, you can check the pH of the fermented cucumbers with a pH strip to determine if the pH is 4.6 or lower. If so, the fermentation was successful. If the pH has not yet dropped to 4.6, allow the cucumbers to ferment for another day. (See Recipe Notes.)
After the third or fourth day, remove the pickle pebbles from the jars and add 1/4 cup of maple syrup (or honey) to each jar. Put the lids back on the jars and refrigerate.
This fermented cucumber salad is best consumed within 3 months.