I cheat when I make French knots. I got tired go them pulling back out so after I wrap the needle and go through the cloth I hold the knot tight with one hand and I come back up through the middle and take the thread over the edge of the coiled thread and go back down again angling the needle to go back through the center. It leaves the knot in place but it anchors it so it can't pull back through the fabric. My knots are not picture perfect but they still give the look.