Step 5 (one through 4 are found in the post below)
pin sides together starting at the crotch and working up to the waist)
baste stitch sides together with dark matching tread (be sure to use a denim or jean needle). I find I often need little adjustments to this seam so it fits just right. once you find the perfect fit seam sides together over your baste line.
serge off excess. if you don't have a serger I recommend you run a second stitch line 1 to 2 mm from the raw edge and then zigzag over the raw edge.
pin serged edge to one side from the right side (or outside) of the jeans. you will be top stitching next. here are views from the right and wrong (inside and outside).
using your top stitching tread run two stitch lines 2 to 3mm apart over the folded raw edge. don't forget that you can loosen the presserfoot tension if the layers become too bulky. If you are unable to find top stitching tread in the right color you can buy regular tread and stitch over the same line 2 or 3 times to bulk it up. I ended up having to do that one these jeans.
reattach the belt loop over the waist band seam line. you may have to do this by hand as there are so many layers of fabric here.
marvel at your before and after. total time = 1.5 hours...so worth it.