Tapering pants properly

Hello! So! I need help with guidance- tapering this pair of pants. I do not need to hem them, however, just taper.

I would usually just flip them inside out and straight stitch at an angle up to the middle. (Or down?).

However, I believe what we see here is a “double feld stitch?” (It appears the same on the top and bottom).

So, what do I do exactly?

I would really appreciate help as I am willing to put in the work to do this properly- so that the seams look the same when I am done.

Thank you dearly!