How to do a corrective trim on a splayed

hoof on a two year old?

Okay, so farrier will also give advice, but at the moment I only have one horse in shoes so he is not here very often. I do all my own trimming with advice from him for problems or corrections.

2 year old colt with a near hind hoof which is splayed on the outside, close to normal on the inside. Do any of you gurus have suggestions for the best way to trim it now to change the way its growing. It hasn't obviously been splayed up till now, but he has become a lot more active recently with a newly acquired playmate.

Any ideas gratefully received.

In general, one removes the splay. (AKA:flare)
Is there a conformational reason for said splay?