I make gathered hammocks and use a strangle knot to tie the ends. I don't need to knot the fabric or embed anything in it; the knot just holds.
The annoying thing about the strangle knot it that it's really hard to break. I use an awl to pry it apart.
I have tried White's Knot (not the gay white knot) and it works well, but I haven't used it in the field yet. I don't have pictures but ...
1 - Take a length of cord and put 2 round turns around the fabric.
2 - At one end, make a turn, and then 2 more, tucking the line *under* the first and laid nicely back towards the center.
3 - With the other end, do the same, working the turns towards the center.
4 - Tuck each of the free ends *under* the *outer* turns. They should face back in the direction they started from.
You need to work this knot carefully into shape before trying to pull it to ultimate tightness.