Among the many issues I'm struggling with to perfect my sourdough batarde is this...

I'm getting good oven spring, but the loaves always expand mostly through the seam on the underside of the batarde rather than the slashes I've made in the top. I'm guessing that I'm doing something wrong in the shaping. I'm pinching the seam closed tightly, but just can't get the perfect grigne.

Does anyone have any suggestions?

thanks in advance

Les