easy-peasy; simple; something that is effortless or easy to do (colloquial, often childish)
この作業はマニュアル通りにやれば楽チンだよ。
This task is easy if you follow the manual.
朝ごはんはパンだけにすれば楽ちんだ。
If you just have bread for breakfast it's easy/low-effort.
その方法なら時間もかからず楽チンに終わる。
With that method it finishes quickly and easily.
comfortable; pleasant; something that feels easy and comfortable (colloquial)
このソファは座り心地が良くて本当に楽チンだ。
This sofa is so comfortable and really cozy.
今日は家で楽チンに過ごしたい気分だ。
I feel like spending a relaxed, comfy day at home today.