Bring the water and salt to a boil, and continue to boil.
Place the cucumbers in a jar or a container. Pour the boiling water directly over the cucumbers.
Keep them entirely submerged in the water by weighing them down with a heavy plate or bowl. When the salt water has cooled down, close with the lid, and let stand at room temperature.
Pour the brine out into a large pot, and boil it for a few minutes. If there’s a while film (golmaji) on the surface of the water, strain it out before boiling. Then, cool completely.
Pour the cooled brine back over the cucumbers. Close with the lid, and ferment at room temperature and then refrigerate. The color of oiji should be between olive green and yellow at this point.
To serve, thinly slice the cucumber and soak in fresh water until the desired salt level is achieved. Sprinkle with some gochugaru and/or sesame seeds and garnish with chopped scallion, if desired.