The main focus with this build and what I'm showing you is to maximize your utilization of your Volley. Playing this correctly can allow you to completely CC your target with the help of Icebourne Gauntlet and your Q with W. She isn't going to be putting out as much damage as AD obviously, but with the amount of cooldown reduction, your Volley will be on a 2ish second cooldown at max level.

With the added AP from this build, your Ult at end game will be doing a good brunt of the damage for team fights. With the added damage from your Volley at nearly 2 seconds of cooldown time, you will be doing more damage than you might think.

Muramana The reason I chose this item first is because of the mana usage of your Volley, and since you will be having such a short cooldown for it, you need the mana. This also arms yourself with the AD you will need for Volley and Auto Attacks to do the damage you WOULD need. This item also has a very strong active, which you can keep on during fights and deal INSANE auto attack damage.

Ionian Boots of Lucidity - Obviously for the Cooldown :)

Iceborn Gauntlet - This baby is your bread and butter. It has the Mana, Armor, Cooldown Reduction, Ability Power, and most of all... Passive JUST FOR YOU! After using W, or with your Q on, you will be AOE slowing and damaging the target for basically forever. Downright dirty.

Nashor's Tooth - This gives you added attack speed, ability power (For your ult) and Cooldown reduction to help you get to 40%.

Liandry's Torment - Believe it or not your W is considered a spell *Come on Riot, give W an AP Ratio*. With the 2 second cooldown, you're putting out the D.O.T from this item permanently on multiple targets, if hit. If you read it's passive, the burn does double damage to impaired targets. Since you are Ashe, with your Volley on a 2 second cooldown keeping someone slowed, it's going to be doing DOUBLE DAMAGE!

Malady - This is giving your auto attacks more force, as well as more attack speed of course.