The simplest way to increase propagation delay is to add a capacitor. I add a tiny capacitor (pf) to make delay on a ALE signal for a microcontroller to algin it with other signals.
Note: you should consider the tolorance of capacitor. also see the signal by oscilloscope.
If the increase is not big a resistor between output and input might be enough.
Otherwise one may need to add also a capacitor at the input to get a longer delay. But in this case, it is preferred to use inverters having schmitt trigger inputs.