Double Sided Alignment? Hello,

I've got a circular part with a hole in the middle that I need to etch on both sides and have it align properly.

My idea would be to cut out the center with a notch and fixture it down to the cutting bed so it doesn't move. I can then flip the workpiece and have it still be aligned.

Any problems with this method? better ideas? I'd rather not reinvent the wheel if I don't have to.