I took another piece of upholstery fabric, wrapped it around my hips and cut it a little wider than that. It was a rectangle 110 cm wide and 90 cm high.
In the back I cut the fabric a bit narrower at the top and sewed a zipper there. The back seam I treated as a vent.
I tried it on for fit and determined how much I had to take in at the top. I made some large darts in the side, where otherwise the side seam would have been located.
This is how long the side seams are. They run well past my hip. They make for a slight A-line.
I added two little darts in the front.
Usually I have to add long darts in the back but because the zipper is on an angle inwards I did not need any darts in the back.
Funnily enough the pattern in the fabric matched just at the base of the zipper. Lucky coincidence.
I caught the top edge in a waist band and finished it nicely. (I’ve been wearing it, that’s why it’s creased.)