Where can I find Blood Stone Chunks?

If you've got access to cainhurst castle, I think you can get 3 from there, can't remember where but you can just follow a guide for that. It is a high level area though so depending on your level you may find it tough. As well as the guaranteed chunks I mentioned, there are 2 enemy types here that can also drop the chunks if your lucky, the gargoyles and crawlers that you see outside the castle door.

If you haven't found any Blood Stone Chunks around the areas you are exploring, you likely just need to advance further into the game. The first one that you can find in the main story areas is in the Forbidden Forest with areas after that having progressively more and more available. Additionally, you can farm Blood Stone Chunks from

the Skeletal Scourge Beasts in Yahar'gul, Unseen Village and the Scourge Beasts with blue eyes in the Upper Cathedral Ward. The blue eyed Scourge Beasts in the Upper Cathedral Ward are faster to get to, so they are generally your best bet for farming chunks.

If you go to farm Blood Stone Chunks, be sure to equip an Eye Caryll Rune if you have one available, since it will make it more likely for the mobs to drop items.