My sister and I experimented with this awhile back -- it's not very hard. I'll try to explain.
I'm not very experienced with sewing, either, so don't worry -- there won't be any sewing terms used, haha.
First, cut the jeans/pants to the length you want the skirt to be,
plus about an inch for the bottom seam allowance (unless you want a frayed bottom -- then cut it to the exact desired length). Then take a seam ripper or use a pair of scissors to carefully rip out (open up) the seams which make up the inner legs and crotch. You will notice that the area which makes up the crotch makes a sideways "V" -- place this over the other half of the crotch so the fabric will lay flat. Pin. Repeat in the back to make the crotch fabric lay flat. You will now see that there is a triangle of fabric "missing" from the center front and center back of your skirt-in-progress. Cut out a piece which will fit and fill in the space, and pin it in place. Now you can stitch along all of the new seams. Try to use a matching thread and follow the previous stitching for the most professional look. When the new seaming is done, turn under the bottom hem
twice (to hide the raw edge) and straight stitch along that bottom edge to hem. If you are wanting a frayed hem at the bottom, cut it nice and even, straight stitch around about 1/4 of an inch from the edge, and then run it through the washer & dryer a few times to fray.
I hope that helps! My sister's skirt actually turned out really cute, and it was her very first sewing project ever.
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