Using a small knife, cut each cucumber crosswise into 2-inch (5-centimeter) pieces. Stand the pieces on their cut sides. Cut each piece two-thirds of the way down into quarters lengthwise, keeping them attached at the bottom. Sprinkle the cucumbers with salt, making sure to stuff inside the cuts of the cucumbers. Place in a single layer on their cut sides in a glass or other nonreactive dish, cover and let sit at room temperature for 1 hour to soften.
Meanwhile, prepare the chile paste mix. In the bowl of a food processor, combine the chile flakes, salted shrimp, sugar, scallions, garlic, ginger, onions and 2 tablespoons water. Pulse until a coarse paste forms. Stir in the chives.
Rinse the salted cucumbers very well under cold water, making sure to clean out the crevices, and shake dry. Spread open the cucumbers and, using plastic gloves, stuff the chile mix into and around each piece generously. Place in a container, packed somewhat tightly, and press in any remaining chile paste and liquid. Seal tightly.
Allow the cucumbers to ferment at room temperature for 24 hours. Refrigerate until ready to serve.