Fly Fishing Knots

I want to know what the proper knot is to use when tying a midge or nymph as a dropper fly under a dry fly. I'm talking about tying the seconded piece of tippet used to connect the dropper fly to the dry fly to the hook on the dry fly. I use 6 or 7x Floucarbon tippet so it can't cut into itself. Right now I use a clinch knot, but it think it's only a 90% knot and I’m looking for a 100% knot if there even is one that is supposed to be used here, if not I think I’ll use a Davy's Knot.

I hope I wrote that so you can understand it, if you can’t then let me know so I can try something different.