The slit is basically a “lined” diamond shaped cut-out in the garment fabric. When folded in half along one of its axes, the diamond turns into a V shape. By locating the points of the diamond on the hem line, the result would be a V shape “slit” at the hem.
The steps are:
- Cut a piece of lining larger than the diamond by 3/4″ on each side of each axis.
Draw the diamond shape on the wrong side of garment fabric, with two of its points on the hem line.
I’d recommend making the diamond larger than the desired slit size by 1/4″, as I find the shape “shrinks” a bit during construction.
- Pin the lining to garment fabric, right sides together.
Stitch the outline of the diamond shape, drawn earlier, pivoting at corners. Use short-ish stitch length, especially around the corners:
Slash inside of diamond, through both layers, from corner to corner:
Press seams open, turn lining to wrong side of garment and press the diamond shape, then fold in half along one axis and press.
Fold along hem line and press and voilà!