You get less distortion the further you stand from the camera (within reason). For a mirror selfie I usually try to stand about 4-6 feet away and then zoom in a little (further might even be better but space and the resolution of my old phone camera don't make that easy). I've found that holding the phone in front of my face generates the best photos and doesn't obscure the outfit. I know conventional wisdom says waist height but at close range I feel this distorts weirdly. My method does foreshorten slightly esp if you are very close to the mirror.
I prefer to take my wiw photos with my point and shoot camera if I have time although it's old and not the best quality. For those I place it on a shelf about waist/chest height and shoot across a smallish room with the self timer. I crop out all the empty space on my computer afterwards.
Also lighting is important. Find somewhere with good natural light if possible and no backlighting. I never ever use a flash.