I was lucky with the build of these jeans that I was able to slice off the legs just above the crutch seam, giving me a straight seam to work with on the hip pieces. The fabric that I bought was 150cm wide and 2 metres long, so I sewed the cut edges together with a french seam to give myself a good wide skirt.
When the skirt piece was sewn on, I folded the seam back up against the denim and sewed it down again to give it a little more strength; hems, they were made for me to step on.
And I have a finished skirt, in a little under an hour. And even better, it has pockets! Skirtage that still allows me to carry my keys and wallet without the need for a ruddy handbag. Suzie approves too, and that's very important.