I can't get a perfect outline to save my life! If it was really important I would probably use mmf and a cutter. Other than that I'd guess I just need to practice!
Practice- or I use a thin royal and just dip the top of the cookie in it, run a spatula around the edge, and let dry before adding other details. Perfect top every time!
I just love your eyeball cookie idea- did you come up with it and do you mind if I use it? They are so cool!
Amber
When the cookies come out of the oven you could press a circle cutter into the biscuit, gently, which leaves a round imprint that gives you a guide to trace round.
Wow,all good advice,I didn't think of any of those and I'm
sure they will be useful. I can't remember if I saw cookies like this or I adapted it from PB eyeballs...... I have so many thoughts always racing it's hard to keep up! 
Pls by all means feel free.. 
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