I have a box pleat skirt that I am putting into production with some small changes. But the pattern has always irked me, as the pleats haven't sat as well as they should. So this is the process I am using to improve the pattern.
I trace the card pattern onto patternmaking paper. The paper is necesary because I need to be able to manipulate it - fold and refold it. The paper is important when the patterns are in development and you need to do lots of sticking, cutting, tracing, etc.
Here I have folded it along the intended pleat lines. You can see how the seam line does not match up. It should form the perfect curve - just as if there was no pleat at all. This was the problem with my original pattern. It wreaks havoc with the hemline too.
I use my french curve and redraw the waist line where it should be. It ends up being about 1cm higher at the side seam. This means I have to also raise the hemline at the side seam by the same amount so the side seam length is the same on the front pattern piece and the back pattern piece.
Then I just have to do this for each skirt size. I've done size 2, 3, 4, 5, and 6 this morning. Now I just have size 8 to go.