To really over simplify this, if the velocity remains constant the higher the G's the faster the turn rate. And inversely, if the G's remains at a constant, the lower the velocity, the faster the turn rate. Corner Velocity is the airspeed at which your aircraft has the fastest turn rate and tightest Turn Radius. This is not the slowest you can fly while pulling back on the stick as hard as you can. You can not pull higher G's at slower speeds.
Less lift is available, therefore there is less force available to work with.
Also, at high air speeds, you are unable to pull high G's. So somewhere in between really fast and really slow is your Corner Velocity. If there is no documented speed in the manual, you will need to play with the handling to figure it out. It also needs to be noted that altitude can affect this figure as well. There are 4 basic means by which you can adjust your airspeed, up or down, to reach Corner Velocity.