This shirt/dress/thing was a fun challenge: I wanted to loosen the neck and lengthen a shirt that already fit (size small, but a shirt from the 80s, so a bit longer and narrower than a 'modern' size small). This should really only be done with shirts that already fit or are too large... anything too small could get really awkward.
Unlike the last dress, there were no scraps left over - 100% of the shirt was used and very little fitting was required. Practical! Basically it's the same cutting as was done on the first t-shirt dress; cut sleeves off, once they're off, cut the under-arm seam of the sleeve. Cut the shoulder seams. Attach sleeves to the shoulder seams! This lowers the front neckline considerably (and turns into the back of the final product unless you're layering!) and lowers the back neckline to a reasonable level for front or back. Stitch up the former sleeve holes to fit; the top of the old shoulder should be about at arm pit level.
The resulting long tunic type thing was definitely not something I'd wear without jeans, but it's not scandalous enough that it'd be inappropriate in public for some people* (depends on your taste!)
Apologies for the blurry comp photos; it has since been gifted to a friend who enjoys the color black, layering clothes, and happens to also be a similar size.