I have continued to "improve" on this. I'm a lazy knitter... Just socks and if I can find an easier softer way I will.
These days for my toe up with flap and generally rib or stocking stitch type socks, I use the half linen stitch just on the sole of the heel (and toe of course) and use the next size needle up just for these stitches worked in this style.
There is no need to work extra rows but it does mean you need to use markers so you know where to make the increases for the gusset if you are making the heel flap type of heel.
You can also make the heel flap itself in the half linen stitch style if you want...sometimes I do.
The important thing is that it works with an UNEVEN number of stitches.
Round 1: K1 [K1, Sl1p wyif] until two sole stitches remain, K2.
Round 2 and 4: K all sole stitches.
Round 3: [K1 Sl1 wyif] until one sole stitch remains, K 1
wyif - with yarn in front
Abbreviations and their meaning can be found in this glossary
This was sock patternwhere I first met the linen stitch