Insert a text box on the slide
Type the time or countdown value
Format the text size, font, and color
Duplicate the slide for each countdown step
Set slide transitions to advance automatically after a set time
Use the Animations tab to add entrance or exit effects
Set animation timing in the Animation Pane
Insert a video or GIF timer if you want a visual countdown
Add a VBA macro for an automatic live timer
Use an add-in or template with built-in timer features
Test the slideshow in Slide Show mode to confirm timing works