Friendly, openhearted, and easy to talk to; showing a frank, approachable manner (na-adjective).
あの店長は気さくで、誰とでもすぐ話をする。
That manager is friendly and talks to anyone easily.
初対面でも気さくに接してくれて助かった。
It was helpful that they were approachable even when meeting for the first time.
気さくな人柄が職場の雰囲気をよくしている。
Their friendly personality improves the workplace atmosphere.