Find a location that has healthy number of bloodstalker, sport a ghillie shit and build a wood base with 4 foundations 1 wall high stick 4 beds inside,preserving bin and a storage box, makes your blood last 4 hours+ enough time to get approx 1k+ blood plus the 4 beds minimum allow you to respawn at that spot continually I've tamed 2 so far with no issues with this method 2 attempts 2 successful tames, once one grabs you and its taming meter appears go into inventory screen and stay on it so swarm doesnt interrupt the taming.

More Bloodstalker Taming & KO Tips