so an embroidery french knot.
Pull yarn out from back (all of yarn
bring tip of needle back to were yarn came out on surface.
USE tip of needle to make a 'stitch on the needle (a simple script E cast on (the stitch is lying on surface,
the yarn is wrapped ONCE (in a script E shape)
hold the yarn (the end of the script E) close to needle.
push needle through, and pull yarn/ (the place the needle goes in, should be close to, but not exactly the same place it came out.
as the last of the yarn travels throught the stitch, a small neat knot will be formed.
if you want bigger knots, use thicker yarns (double) do NOT Double WRAP
(this is how i learned, on PBS, from Erica Wilson (of crewel embroidery fame) some 30 years ago.
the single twist and holding yarn close to stitch as you pass needle through is what makes it work.