Countdown macro help.

I'm not exactly sure where else to post this, but when asking elsewhere, I didn't get an appropriate answer. And I still am technically new, as I still have a sprout leaf.

I was running with a tank in an instance, and before every boss they had a really interesting way to do a countdown. They would pop the target to attack 3, 2, and 1 over themselves before pulling, and I'm wondering how to go about doing this? It was very visually appealing and helped me immensely. I've tried a few ways to go about it but I keep getting errors and it doesn't mark me so I can test it.

I realize that a 10 or 15 second countdown is better and it only REALLY matters in ex/savage stuff, but I really do just want to know how it was done, at the very least!

Looks like this thread covers what you're looking for. Although, these solutions are largely obsolete with the introduction of the actual Countdown command. But, should still functionally work as an alternative.

Use

/cd 15

This is the built in countdown timer.

Its one failing is that it can't be used once someone has aggroed the mob. This is not a problem most of the time, though there are a few fights where it could be helpful to have a custom countdown macro (e.g., Chadarnook (Sigmascape v2.0) becomes targetable 17s after someone crosses the center of the room, but if you miss your chance to /cd 18 as someone starts running up, you can't use the built in countdown anymore). However this sort of thing is rare, and you'll be fine with a /cd 15 most of the time.

Just know that you should start at 15. Starting at 11~14 will skip the 10s warning, and all they'll get is the warning that a timer started, and then a 5-4-3-2-1.

Thank you both for your answers!

I'll probably never tank seriously, and definitely not in a raid or in extreme/savage content. I just thought it was visually appealing and was simply curious as to how it might be done.