How to direct teammates and avoid flaming?

I find it helps to phrase directions like that as a question. It makes it seem more like I'm asking for advice or discussion rather than directing the team.

"We have good poke. Should we try sieging instead of teamfighting?" "When is your TP up? It might help if you splitpushed to draw people away." "Do you think we are safe to do dragon?"

Alternatively, you could just state something you think is obvious or a direction as an observation. "They are probably going to gank top soon." "They are always in our jungle. We probably need more wards out." "I think their [] buff is spawning soon. We might be able to take that."

In your case: "We are probably strong enough to teamfight. Maybe we should just group and push." or "Maybe we should roam their jungle as a group to get a pick."

There is absolutely nothing that can possibly be said to direct your teammates without flaming.

I'm not even joking.

Furthermore, they could be intentionally throwing the game, and the only person who is going to be punished for it, is you, because you flame.

I guess, when in Rome, join the meta, ???? + roll of the dice = 50:50 (I hope the enemy gets more retards than I do). There is no actual strategy, despite the game being a strategy.

You really can't. The only thing you can do is play well and try to exploit the enemy response to your teammates fail. Also, if you do really well they will start following you around since their thing isn't working out.

Most of the time they aren't purposefully trying to die. They just aren't calculating the risk vs reward correctly.

Words matter, and how you phrase the exact same sentiment can dramatically change how it is received.

Let's say your teammate keeps trying to split push and keeps getting caught. You could say something like: "You need to stop over extending and dying, it's costing us the game!"

OR you could phrase it a little differently like so:

"We need to group up and take advantage of our lead. That'll stop us from getting caught. Let's group and take objective X"

Notice how I'm saying the same thing, but now it's WE instead of YOU. This spreads the burden of blame amongst the group and stops players from going into defensive mode. This also phrases it in a way where the player knows you still consider them part of the team, and want to work together to win. Cherry on the top is offering a clear solution to the problem and a path to victory (group to stop dying alone so we can take objective X).

See what I mean? Started changing my words in all chat like this, started winning more games. Words matter!