In a small bowl, add rice vinegar and honey. With a spoon, mix to dissolve the honey into the vinegar. Add fish sauce and lime juice. Then add vegetable oil and red hot pepper flakes. With a spoon, mix dressing. Leave dressing aside. Slice ends off of the cucumber and slice cucumber into thirds. With a mandolin slice cucumber into julienne pieces. With mandolin, slice onion into thin julienne pieces. Dice your scallions. In a large bowl, add cucumber, onion and scallions and drizzle in some of the dressing. Toss with tongs to coat salad with dressing. Serves 2-3.