There are many ways to teach a box turn, some work better than others. I've tried several different methods over the years and am still open to trying new things. My favorite methods are either the wall to a ramp and straight to the box OR the chute, to chute with ball, to box with board, to box with ball. Either way I like to start with lots of "over and backs". The choice to do train a wall turn is usually determined by how much someone is going to be doing at home. If the handler doesn't do much training at home, I have a really hard time training the wall only once a week. Also some people are turned off by the wall because of perceived safety issues.
I wish I had video of Indy learning her box turn. I had no idea what I was doing at the time. We used a square board the size of the front of the box (training board) and taught her to hop on that (with the board on someones lap) and get a ball. Somehow she has an excellent box turn now. I later used the wall and various up close box work drills to speed her up. Some dogs are very forgiving. Here is the earliest video I have of her of her turn.
I recently had a reader ask me this question about an 11 month old border collie in training....
slowly been introducing the different stages of flyball. She
has a really good box turn and will return to the handler over all 4
jumps. We introduced the ball and she did a good job 2-3 times. One
time she hit the box prop and since then will not go to the box if
there is a ball in it or if she does she will lean forward and try and
steal the ball (won't jump on the box). So we have been having her run
to the box and do her box turn then back to the handler.
This is one method that I have to say I don't think it great. I think "hit its" are okay in moderation to get the dog used to the box, but not to the point that they start to build muscle memory for a box turn with no ball. It doesn't really count as a box turn until there is a ball involved. Without a ball, the body positioning is completely different. I also don't like the idea of building up to full runs without the introduction of a box turn with the ball. With the full run you are introducing speed and striding and it will be off if the dog is just hitting off the box without catching a ball.
In this video you can see that Pax's head isn't going anywhere near where it should be to catch a ball. This is teaching the basic body movement, but shouldn't be done too much and especially not directly on the box.
For the particular dog mentioned above I would probably work with a chute with a ball velcroed to get her comfortable with grabbing the ball without having to worry about it coming at her. Once she got this part, I would introduce the ball on the box, but I'd rest it on the ledge with a board leaning up on the box or jam the thrusters so the ball can't pop out. I'd also work on dead ball retrieves over the box prop and general ball catching practice.
If the issue is with the sound of the box, it would help to bring the box home and desensitize the dog to the sound by click/treat when the box is triggered.
The other methods I've seen to teach a box turn have not been successful for the most part from my observation. I especially don't like the introduction of the box before the dog has the body motion with the use of lots of a box props to get all four feet up. These are the dogs that lose their turn with no props. As I've mentioned before I'd like to try shaping a box turn with a clicker, but I'll probably have to experiment on my own dog to try that!