The layback is a classic, glamorous element. Executing it to wow the audience is tough though: sort of like an animated cartoon, it frequently looks crude (like yeah, she's doing a layback) or it falls in the broad range of good enough, without being anything special.
You can impress me with either of the two forms of this (not both at the same time though please, choose one or the other). The first I'll call "beachball," the second is "armfully elegant". First though, a sideword about physics. Since your layback posture is rather precarious, you need to be positive you are precisely centered on your spin. Even the slightest amount of precession will bosh a layback.
Secondly, please enter your layback with some panache and gradualness. It looks awkward when a gal just suddenly snaps back -- yeah I know you can do it and it shows off how flexible you are, but it's not very graceful.
"Beachball" layback is the standard circular arms pose: I liked to tell my daughter to imagine grasping a large invisible beach ball. Do you see the image at the top of this blog? Yeah, like that. For the optics on this to be correct, it should appear that the virtual center of the beachball stays absolutely fixed as your arms rotate around it.
Shoulder position is paramount on this layback, and is where most skaters don't quite achieve perfection. Ideally your shoulders should be back parallel to the ice, with both shoulders at the same height. When you are rotating though it's nearly impossible to judge this by feel alone: you really need to have somebody video your laybacks while you're practicing to get the alignment correct.
The other layback, armful elegance, involves weaving a pattern with your hands, arms, or both, as you are spinning while tilted back. The art in this is to be graceful yet with purpose: not too much arm action, but something to tease out the spirit of your music or what you wish to express. I've seen this performed with arms flayed to the sides, to reveal a blooming flower, perhaps. Or up in gentle fountain like flares.
As you make progress through your rotations, naturally you must slowly lower your back off-ice foot so as to capitalize on its storehouse of angular momentum, thus keeping your rotational speed constant.
It takes an extreme amount of polish to change your average layback from something you just do to complete an element, over to a spectacular expression of an artform. We don't just want to see that you know how to do a layback. We want to be entertained.