This is the 4984th most frequent Japanese word.
細か
Detailed; fine; minute.
In this sentence, 『細かい』 describes the noun 『計画』 to indicate its detailed and meticulous nature.
彼は細かい計画を立てるのが得意だ。
He is skilled at making detailed plans.
Here, 『細かい』 describes 『デザイン』 to highlight its fine and intricate aspects.
服の細かいデザインがとても美しい。
The intricate design of the clothes is very beautiful.
In this case, 『細かい』 is used to refer to trivial details, showing its usage for describing small or insignificant aspects.