Nice work, cool designs. Cork is satisfying because it engraves so dark with so little power.
As for alignment, I’d recommend using a corner jig. The basic process is that you draw a full- scale outline of your trivet in inkscape along with your design, then make an L- shaped path that touches two points on the circle.
You place cardboard or something cheap in the gf, load up your design and then cut the corner off so your L is right where the trivet needs to be.
Open the Glowforge, slot in the trivet so that it’s seated in the cut corner jig, turn off the L-cut and turn on the engrave. The alignment will be dead center perfect every time.
Do not trust the camera, trust your jig. Never move the art and have faith 
Here’s the process illustrated:
Enjoy, jigs are a piece of cake, you’ll never look back