For this I used bias tape hem facing. You don’t have to, but I think it makes it so easy.
Measure from the top of the slit to the bottom of the hem and cut the hem tape to that length. I added an extra three inches to the top just to be safe.
You’re going to sew the bias tape over the existing slit seam allowance. In this picture I unfold one side to show you. I sewed right on the fold from bottom to top on both seam allowances.
This is me sewing it. I moved the bias tape to the left to show you what I was doing. I’m sewing on the fold about 1/4 inch from the fold of the slit.
When you have both sides done and you fold the bias tape on it’s fold, it should look like this. It should look like it has become the seam allowance that was previously there.
Cut out the seam allowance from underneath. I cut along the edge of the bias tape. (I had not unpicked the lining from the seam allowance yet. I did that next. It’s easier to just unpick it all at the beginning.)
Now you should have two seam allowance pieces and two bias tape pieces that have replaced the seam allowance pieces.
Sew the two seam allowance pieces together make one rectangle of fabric with a seam down the middle.
Now you’re going to sew this new rectangle to each side of the bias tape, right sides together.
You’re almost done! this is what it should look like.
Now reattach the lining. The lining is going to be sewn to the top of the box pleat.
To make sure you don’t sew onto the skirt, sew the lining to the top of the box pleat starting at each side and going towards the center. Make sure you’re only sewing through lining and pleat, not through the outside of the skirt.
The edges of the lining can be turned under and sewn.
Don’t forget to rehem the skirt where you unpicked. You should hem through the pleat so that it doesn’t have a raw edge on the bottom.
I hope this makes sense! Here are two other examples: purple dress and white dress. I love the look of this box pleat and hope others can save their skirts using this. Ask me if you have any questions!