Tracking their Flash

Note when they Flash: about five minutes to punish it.

From Platinum

Professor Zéphyrinthe Academy's instructor

« Notebook out: their Flash just went down? Type the time it comes back in chat, and your jungler knows exactly when to strike. »

They burn Flash
You win the trade; to get away, your opponent Flashes. Their Flash goes on cooldown.
Note the time
8:10 on the clock: it comes back around 13:10. You say it in chat, so your jungler knows too.
The window
Your jungler comes: without Flash, your opponent has no way out. The kill.
It's back: respect it
13:10: their Flash is up again. The window is closed: no more all-in counting on it.
The classic mistake
You forgot the time. You all-in with your jungler: they Flash away, and the gank was for nothing.

When to do it

They Flash to escape: note the time right away, before you forget.
Your jungler is nearby: a laner without Flash is a gank waiting to happen. Tell them.
You have kill pressure: without Flash, they can't dodge your all-in. That's the window.

Type it in chat: the role and the time it comes back, about five minutes later ("mid flash 13:10").
Check the clock before an all-in: is their Flash still down?
Track the other spells too: a Heal, a Barrier or a Cleanse on cooldown also opens a window.

The classic mistakeForgetting. Five minutes later you all-in as if it were still down: they Flash away, and your jungler came for nothing.

Good to knowSome items and runes shorten summoner spell cooldowns: the five minutes are a guide. When in doubt, count a little less.

Iron to Silver

When your opponent Flashes, look at the clock and say it: one line in chat is enough.

Gold to Emerald

Write the time it comes back, not the time it was used: your team has nothing to add up.

Diamond and above

Track every summoner of your lane and of their jungler: plan your all-ins and your jungler's ganks inside the windows.