Power Surge method for training turns.

The humans in these photos prefer to remain anonymous.

The dog is Sky, a Border Collie owned by DogGoneFast member Bill Payne.
You need two jump baseboards fitted together at the notches so they form a right angle. If the dog turns to the left (from the perspective facing the box), place the boards in front of the box (closer for small dogs, farther for big ones) with one leg parallel and the other perpendicular. The perpendicular leg should be lined up at or near the centerline of the box. Have a person stand in front of the boards with their left foot at the end of the perpendicular and their right foot one step behind, blocking the dog from going to the left side.

The dog will come up the right side and the boards will force her to jump, but she will have no place to land but on the slope of the box. After the dog passes, the blocking person steps forward with the right foot, getting out of the way of the dog, who has hopefully just executed an excellent swimmer's turn. For a dog that turns to the right (again, from the perspective facing the box), just do a mirror image of this technique.