Wash and scrub the sweet potatoes clean. Peel them and slice them into evenly thin rounds using a mandolin or knife. Ideally you do not want very large rounds. Otherwise cut the sweet potatoes into three or four pieces lengthwise. Then use a potato peeler to cut long and thin slices, like I did. Make sure the slices are dry. Pat them dry with a kitchen towel, if necessary.
Dissolve the salt in the water and keep aside.
Heat a largish wok or pot half filled with oil (or coconut oil) over a medium to hot flame. When the oil seems hot enough (not smoking hot) drop a sweet potato slice in it. If it bubbles vigorously and comes up, the oil is ready for frying.
Carefully, drop a small batch of sliced sweet potatoes into the oil. Immediately add a couple of teaspoons of the salted water. Stand away from the wok while doing this. Since the sweet potato slices would have brought down the oil temperature a bit, the water should not cause the oil to spit too much.
Flip the chips every minute or so, until the bubbling dies down significantly. The chips should turn crisp up with the edges curling a bit, turn golden brown, and make a sound as they rub against each other.
Remove the chips from the oil with a slotted spoon, and drain on paper towels. Once they cool transfer to an airtight container. Let the oil come back to desired temperature and similarly fry the remaining sweet potato slices.