The BoRK can come in as early as second item but ideally third or later.
Basically, a full energized build with great waveclear, relying on my runes (taste of blood, ravenous hunter, legend:bloodline, and fleet footwork) for the healing, good attack speed, eventually 100% crit, good movespeed, and reasonable attack damage. I could of course sub out stormrazor for phantom dancer. It achieves much the same; instead of slowing them down super-hard, it speeds me up; it gives the same 25% crit, while giving that shield at low health.
The cheapest of cheap build variants on this, Statikk+RFC+PD+Runaan's+Boots+BoRK is 14,600 at full full build of six items, with the core build being online at like just over 5k gold. Of course, the more expensive build is Statikk+RFC+Stormrazor+Runaan's+Boots+Bloodthirster, which would be an extra 200 from Bloodthirster over BoRK and an extra 800 from Stormrazor (for the total coming up to 15,600), but that's obviously harder to achieve.
Honestly though, just getting the vamp scepter in of itself with the runes to heal and a little bit extra from the vamp scepter can do a lot. Bloodline caps out at 12% lifesteal, vamp scepter in of itself at a cheap 900 gold gives an additional 10% on top of that. Finishing BoRK only gives 2% extra. (Though obviously, Bloodthirster gives double, 20%.)
It's less effective a build at keeping me alive once online, but it gets online much earlier and given how poorly most of my games have been going where I can't build so much as two items before the game ends in most cases, I think it works well enough.
I'll still run the lifesteal build (albeit using fleet instead of conqueror, because, again, need extra laning phase help and conqueror for ranged is getting nerfed) in some matches, where I feel like if I don't have the healing, I won't be of use later in the game, but usually, I will take this build to help me be useful earlier in the game.
Is it the best Ashe build? Oh heck no. If you want to build 100% crit on Ashe, it's probably best to be Essence Reaver, Infinity Edge, Runaan's Hurricane, and Phantom Dancer, for instance. And, heck. You probably shouldn't be building 100% crit on her anyway. Generically speaking, Essence Reaver (an amazingly powerful item) is a good grab. Trinity Force is the meta second grab item, but also good grabs are Blade of the Ruined King and Runaan's Hurricane. So six items would probably be something like a generic boots+ER+Trinity+Runaan's+BoRK+sixth situational item. PD/GA as probably two common ones, though Infinity Edge is also strong on her.
So in an optimal Ashe build, while there's definitely crit, it's 50 or maybe 75%, not 100%.
The runes aren't terrible on Ashe, either, but aren't ideal either. With the nerf to volley increasing its mana cost, Ashe pretty much needs manaflow band to not run short on mana. (Essence Reaver helps due to its passive and the bonus mana from trinity force helps that even more, but even with those items, without manaflow band Ashe will still often come up a bit short on mana in extended fights from what I've seen.) Which means sorcery needs to be either a primary or secondary rune page. Inspiration has multiple good keystones which are very strong. I prefer magical footwear and cosmic insight, but most players take only one of those and then use biscuit delivery instead, again, to presumably help her with her mana shortage issue. Some take it further and use timewarp tonic, too.
So sorcery/inspiration is the best runes overall to use on her most of the time. They're not the only runes to run, but they're probably the best runes.
Still.
I like this build. It's a lot less fun than the lifesteal-oriented build. The absolute most fun is full lifesteal with it still being a blast to do the hybrid lifesteal build. But while it's a lot less fun, it's a lot easier to pull off and is still fun. It's not really the meta build for Ashe, and it's something which I still came up with, and it's proving reasonably effective, so I will probably keep using it.