To make a Countdown Timer display on your Echo Show, say “Alexa, start a countdown time for ‘X’ minutes/hours.”
Once the timer has started, it will show on the screen very large for a few minutes, then go to the top right corner once the Echo Show returns to the Home Screen. During the last few seconds of the countdown timer, an animation will appear, displaying how many seconds are left.
Hope that helps you!
-Daniel