How to use ES as supplementary defense?

I mean not as a replacement of your life pool, no CI, no low life. Something like 3-5k life with 1-3k ES. With armor and evasion you can start with small amounts and rely mostly on your life and slowly build your defenses up. But with ES? You can maybe make use of it as a summoner since you don't get targeted much.

Other than that, you will probably need Ghost Reaver and Vaal Pact to counter the adverse effect on your life leech rate. But if you're already near the Scion life wheel and near Ghost Reaver, why not just be a life build with Acro?

Life/Acro gets you better avoidance while CI gets you better damage buffer. A life/ES build be some kind of middle ground.
Maybe you want to do this when you use something that doesn't work well with Acro: block or armor or both. But low amounts of armor and armor in general is considered subpar nowadays, and building high block is much more costly than Acro.

Maybe something along these lines?

You can just have gear with ES on it, you just can't regain the ES shield if your constantly getting hit. Something like a 500 shield + a ton of int will give you alot of ES.

There is no reason in specializing more into ES outside of that since you can't regain it.

If you have some ES just get Ghostreaver and be done.

If you dont get Ghostreaver or dont have enough leech for it just go EB and get more mana reg.

Having ES without Ghostreaver is just a waste... if you can´t refill it during combat its good for nothing imho.

I have 4.3k hp and 1.9k es and no defense aside from a wall of meat and bones ( zombies and skeletons). its all about those one shot and with so much es and hp I can take a 6k hit and live another day

So many people dismiss The Dark Seer, but it's perfect for making otherwise impossible forms of defense possible. So, yeah, try a dark seer or better yet, two of them.

Yeah I'm personally not a fan of on-kill sustainability since it won't do anything vs the most difficult bosses. Besides temp league players are extremely unlikely to get a Dark Seer.
Rest of the responses already addressed in the OP.

Yes I'm aware. But that's not really using the ES, that's using block and BoR.

You need at least ~2-3k es or it's completely pointless.

I did this with my Flameblaster back in beyond with using Zealot's Oath because

1. Life leech not good with Flameblast
2. Flameblast can reflect a lot to you if you screw up
3. Flameblast done as lifebuild with high mana regen goes next to very good ES notables and ZO.
4. I found this

I had like 4k life and 5,5k ES with Discipline (so ZO actually makes life regen better) with 5,8% life regen from passive tree. Could still use life potions for defense while also having a regening and quickly recharging huge ES pool, also the life leech from Catalyst (or crafted with Catarina) doesn't go to waste since chaos damage and occasional spikes will still reduce your life.

Never came close to dying to reflect, a blue pack of devourers did it though.