I seldom describe my characters to the readers; other than traits that are important to the plot, or are already obvious by the plot. Even then, I strive to have other characters make comments on their appearance or looks, and those in somewhat general terms. Or their appearance enters into the thoughts of the POV character.
Readers develop their own ideas, and I think this makes it easier for the readers to identify with the characters they like, and imagine what they will.
One thing I do is find a way to quickly indicate gender, but that might be done by name, or if the name isn't gender specific (or is not usually used with the gender) then with a pronoun. e.g. "Charlie was washing her hair".
Other physical traits can be important to the plot, and should be brought up long before they are necessary. If a person is particularly tall, and that comes in handy, we should know it before we imagine a person of average height. The same for athleticism, or widely perceived beauty, or anything else out of the ordinary.
But I try not to have the narrator do that description; I prefer to invent some situation so the characters do it.
Marcie said, "If Alex were here, I bet he could reach it."
"And if we had a ladder we could reach it, but we don't have Alex or a ladder, so -- any other ideas?"
We also have self reference:
"Oh my god, I love this dress! Do you love it?"
"On you, sure. You have a bust, I can't fill it."
Readers can get a sense of what a character looks like by how other people in the story treat the character, and how the character thinks and behaves. I prefer to leave it at that.
Of course, all that might be ruined by your cover art showing a depiction of one or more characters!