Start from a basic block.

Taper the skirt at the knee and flare at the hem, both at the side and at center back.

Draw the hem of the shorter skirt.

Trace a copy of the upper skirt and draw the panel slash lines.

Make sure one passes through the dart edge so you can manipulate the dart.

Cut through the lines to separate the pieces.

Close the darts.

Flare all panels at the sides by the same measurement.

Here is the pattern of the skirt top layer.

Get a copy of the basic skirt, flared at sides and center back, and cut through the knee line.

Draw the slash lines from the knee to the hem and cut.

Open the new volume on the bottom part of the skirt and redraw its hem.

Here is the finished pattern!