Altering speed of podcast playback on iOS 11.4.1
Assuming you're talking about the default Podcasts app, this still has a 1x option located at below-left of the screen (just below the volume slider on the main page of the episode you're listening to).

Tapping on the 1x option will cycle the options from 1x to 1 1/2x to 2x to 1/2x and back to 1x.