What a useful technique this is! Use it to make a tidy eyelet that looks exactly as thought you'd worked a regular yarnover in the previous row. These afterthoughts tend to be a bit smaller than traditional yarnovers are.
Making an afterthought yarnover is easy. Just lift the strand between the right needle and the first stitch on the left needle, and work into it without twisting it.
(If the strand was twisted, it would close the loop, and then that would be a M1. We want to keep this loop open.)
The tricky part is, if making a series of yarnovers, finding the right strand to work into may be difficult.
Be sure that the strand you're lifting is the same strand as is worked through the other stitches on the left needle.
To work it untwisted, insert the left needle from front to back. The strand will sit on the left needle with its right shoulder forward as shown in the previous photo ... work it through its front loop.
Or if it's easier for you to lift it with the left needle from back to front, then the strand's right shoulder will be to the back ... work it through its back loop.