expression, godan verb (-ku)
get used to a role; become second nature; be at home in a role
Idiomatic expression originally from the theater, meaning that an actor's performance has become natural and polished, as if they are at home on the stage. Now used broadly for any skill or role that one has mastered to the point of looking effortless.
彼の司会ぶりはすっかり板についている。
His hosting style has really become second nature to him.
The new employee has gotten used to the job and is performing naturally.