Work with the front piece
Fold front piece in the center; the bottom must fit on top of each other.
Draw a line in the fold. Cut the line.
Now there are two pieces. Make a parallel spread of 0.5 - 1 cm, depending on the fabric, and tape the two pieces together again.
The spreading is what is sewn to make the fold.
Press both front pieces.
Fold front piece on the center; the bottom must fit on top of each other
Press the fold straight and sharp.
Sew the pintucks
Sew along the folded edge 0.2 cm from the edge