To my knowledge, (and in my own opinion, YMMV) you cannot control temps in a crock pot. I know people have modded them to switch on and off with a more precise thermo, but it's still not as precise as a real sous vide. I use crock pots a lot, but at best they are ball-park temp wise. Low, medium and high can vary wildly. Circulation is key to the process to ensure even cooking. I suppose you can throw in a fish-tank-type circualator, but by the time all is said and done, a $99 Anova will run circles around a crock pot.