Sewing Method, mock reverse coverstich on a home sewing machine.
On my inexpensive Walmart Brother Project Runway CE1100 (bought on sale for about $100). The best choice is stitch number 52, with a stitch length of 2mm and width of 7mm, using a basic cone thread 100% poly.
Every machine make and model is different you may get similar results using similar stitch and setting, but likely will have to tweak them a bit for best results with your machine.
First, do a construction seam as usual, but with a scant 1/4″ or 5mm seam allowance. Then flip to the right side to topstitch with the decorative stitch. I finger press open the seam on the wrong side before I start stitching.