expression, adverb
without mistakes; flawlessly; smoothly
Describes doing something competently and without errors, often implying a natural, effortless manner. Related to the noun そつ (mistake, slip).
See also: そつ
彼は難しい仕事をそつなくこなした。
He handled the difficult task flawlessly.
そつなく準備を進めて、当日は問題なかった。
We prepared smoothly, and on the day there were no problems.
そつ is a noun meaning 'mistake' or 'slip'; そつなく is the adverbial form meaning 'without mistakes'.
完璧に means 'perfectly' and is more emphatic; そつなく implies competence and smoothness rather than absolute perfection.
Derived from the noun そつ (mistake, slip) with the adverbial suffix なく (without). The kanji 卒 is an ateji (irregular kanji usage) and not etymologically related.