Just Jeff says (to attache the hammock rope to a carabiner):

"Put a carabiner on the tree huggers, then just a “double slip knot” in the Spectra. It's basically a half-hitch inside a half-hitch. It holds and it’s quicker to tie and adjust than the Hennessy hitch"

I'm not quite sure what that means. When I try to make it up, based on the picture and the words, I end up with those two loops, but one is doubled.

I tied first a slip half hitch and then a second slip half hitch using the loop from the first half hitch. Is that correct? Again, though, I get those two loops but one is with a single strand of rope and the other is with a double strand of rope.

In any case, this knot I've just described would seem to work just fine.