This is pure theory crafting nonsense, but I have come up with this:

It could use some optimization to maximize the potential of the combo. Nevertheless, here it is.

Ornn has his unique "Brittle" passive that reduces tenacity by 30% (I don't know how exactly Brittle extends CC, so for the sake of simplicity I'll just throw on 30% to the duration). Yasuo has a knockup, and his R is a knockup extension which synergizes nicely with Ornn. Morgana is essentially CC incarnate. Malzahar only has one CC and that is his R, but it's 2.5 seconds long and is essential to get his teammates' CC abilities time to cool down. Neeko has both her R for stun and E for a root.

Malzahar, Morgana, and Neeko will build Everfrost. The rest of their items will be CDR/Ability Haste. Morgana should have blue buff. Yasuo can build whatever he wants, we only really need him for the Q2 and R knockup. Ornn is similar, he will just go his typical build.

Now we begin.

• Ornn engages our victim with Q-R-E-R2-W combo. Depending on the execution of the combo we can get a solid 3 seconds of airborne here.
• Morgana syncs her Q with Ornn's W. Brittle extends Morgana's 3 seconds to 3.9 seconds. Brittle is consumed, Morgana starts R.
• Morgana pops Everfrost just as the root on Q ends, giving 1.5 seconds after which Q should be off cooldown. Morgana Qs again, and R detonates. 4.5 seconds of a root and stun.
• Now that Morgana is down an R and Q, Malzahar comes in with his R. 2.5 seconds.
• Ornn uses W to apply brittle as Malzahar's ult ends.
• Morgana lands a Q, and consumes Brittle. 3.9 seconds.
• Neeko uses Everfrost. 1.5 seconds.
• Assuming Neeko has minions to empower E off of, the empowered E will land with 3 seconds onto the CC chain. This is when she starts her R, and lands the 1.25 seconds of stun.
• Morgana may land her Q again. 3 seconds.
• Neeko may land her E. 3 seconds.
• Ornn lands his Q-W-E combo. 1 second of airborne.
• Yasuo would have stacked his Q2, and just as the victim lands after Ornn's CC he will use Q2 and R at the last second. I would give this 1.8 seconds of CC.
• Morgana may land her Q again. 3 seconds.

Now for some math. 3 + 3.9 + 1.5 + 4.5 + 2.5 + 3.9 + 1.5 + 3 +1.25 + 3 + 3 + 1 + 1.8 + 3 comes out to:

36.85 seconds where the victim literally cannot move

Now as I was writing this, I realized it was possible to indefinitely chain Morgana Q and empowered Neeko E. But then I would have to consider mana costs and how many of them can be thrown out before they literally can't cast them anymore because they don't have the mana. Unfortunately, I'm lazy. But it's a possibility.

I would love to see what you guys can come up with, or if I should swap out some champs to make this even longer.