Titanite Slabs in AoA DLC1. You’ll get the first slab during the Sister Friede boss fight. After you’ve completed the second phase by killing Father Ariandel, you’ll automatically gain a slab. You won’t lose it if you die, but you won’t get another one the next time you fight. Basically, it’s a one time thing.
2. After the boss fight, travel to the Corvian Settlement bonfire. Leave the building and turn right. Go into the house where the friendly Corvian was when you first arrived. He is now standing on the terrace. Talk to him, and you’ll get another slab. We’re not sure if it makes a difference, but when we first talked to him, we told him we were Ashen.
3. The third slab is in the Depths of the Painting. Travel to the bonfire, then find a giant ladder leading up from the frozen floor to the top of the cliff. Climb it, then another, smaller ladder. You’ll end up on a ledge, where you’ll find a corpse with the slab, propped against some red stuff.
You can use them on both the new weapons and the old ones, there’s no difference. There may be other slabs in the new map, but these are the ones we’ve found so far. We’ll update the guide if we find any more. If you know of a location we haven’t visited, leave a comment and let us know.