The build may strike you as odd however let me explain it all to you.

>Sickle Start over Spellthief Edge
Sure, Spellthief is better for mana regen during Items 1 and 2.. However when maxed they both give 100% mana regen. And the extra AD from Sickle will make your volley hurt that little bit more during laning.

>Boots rush
Ionian boots give a filthy amount of CDR.. And you wanna be shooting off your ult as much as possible. You should be able to back for them around when you hit 6.. So recall, grab the boots and start blasting ults all over the place.

>Liandry as the mythic
Liandry's Anguish gives you bonus CDR to all other items, While also giving you some extra tick damage to anyone you hit with your volley or ult. While not an amazing amount of damage due to not going full AP, the bonus CDR is very nice and with how low of a CDR your W ends up being.. you can have the effect on them permanently.

>Cosmic Drive, Wardstone, Quickblades
These 3 items are what I have found to be the best for CDR, While also complementing your build.
Cosmic Drive will give you some extra move speed and bonus AP for Liandry tick damage.
Wardstone is a solid support item as is for vision warding.. And also gives you a big thwock of stats after the rework.. all good stats.
Quickblades very rarely gets built.. And is mainly built just to boost W damage a bit more, and again for the CDR. Other stats are not nearly as important.

Im no guide expert but hey ive had some great success with this build and so am sharing it with the world.

At the start of the game you wanna try and proc your W with a soft invade to try and get manaflow stacking nice and early. Preferably get two hits with it if you can as that will leave you a good bit of time to regen your mana. Your main early drawback is lack of mana without manaflow stacked.
Then during early laning phase just harass using bush to block sight and again, Using W when manaflow is up and ready.

An ideal game will have you finish your manaflow around 4 mins in, and your quest by or before 6 mins in. Of course this wont be every game depending on comp.. But this is the ideal.

Support Ashe shines where you are either kiting back or chasing someone down. Lategame your W will have around a 1 second CD and will be your basic attack leaving your foes perma slowed.. Your E is perfect for scouting ganks around the map and your ult will be on a 20sec cd (not including wind drakes) meaning great ganks (assuming you can land the ults) all game getting everyone ahead.
Its not as explosive as full AP ashe but its still pretty good imo.

The one main drawback of this build is the lack of antiheal, as no antiheal items give good CDR.. However if you are with a Sera APC then they should build Chemtech for the teamwide antiheal anyhow. Otherwise you just gotta hope if you need anti, your team has it covered. (Also why Ignite over Exhaust.)