You don’t necessarily have to write down every little detail about them, because those things should just come naturally to you. Usually, when I create a character; their appearance gives me an overall idea of what they’re like, and I just go from there.
Of course, this isn’t always the case, but it helps to have the basic structure (such as backstory, age, height, and personality) also, moodboards can be a big help in creating the character’s aesthetic/vibe! 