The problem is physical description is not characterization (in my opinion),
This is true of who is being described. However if, as said upthread, you are writing close third/first then what and how someone is described can be characterisation
of the describer. What they notice, how they describe etc.
To the OP, if you keep it in voice, rather than a list of attributes, and show how the person affects the describer, then the reader should know at least that your POV person thinks they are hot, and why.
So: She was five four and a redhead, with pale skin and trim ankles. That's not really giving much of a vibe about the person (describer or decribee) though no doubt for some styles/people to intro it would do.
I would describe her, but all I can remember is the split in her skirt that kept sliding backwards to expose pale skin and stocking tops.... <-- this tells you volumes about the describer, not much about who is being decribed apart from the POV character is rather mesemerised by her and therefore probably thinks she is hot.
Alternatively, describe the way they move, or other things that capture the essence of a person.
An excercise I've found very helpful is to take a notebook, go to a cafe and try to capture a person in three sentences. No cheating with run ons. Pick two or three telling little details about them - the way they run their hand through their hair, the little bobbles on their jumper that they pick off in a nervous habit kind of way, the air of that man over there who looks like he's communing with higher spirits. If attractive, determine what is it about them that makes them attractive as opposed to just good looking (there is often a difference)?A grace in movement? A fluid gesture? An air of self confidence?
Describe what it is about them that is the essence of their attractiveness.