Three main parameters set the oscillator. The period of %K line defines the range that the indicator will use to compare the current price. The %D line period determines the smoothing of the %K curve to get the slow stochastic.
The slowdown smoothes the major period of the %K line, thus, affecting it. For short timeframes (including H1), the standard settings are (5, 3, 3) or (7, 3, 3). (9, 3, 3), (14, 3, 3) and (21, 3, 3) settings are useful on H4, daily, and bigger timeframes.