You can check some of my posts for how looks as a finished product put together, but may not be super helpful. I used the below but wireless interference th a few hand twists.
Countersinkcountersink bit
oh and if you care enough, you can clean up the pin holes and countersink them. Ive done this on all my builds and it looks so much better. 1/2" countersink drill bit, just lightly hand twist a few turns and you're good.
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If i were you i would go with the Chamfer tool.. Your going to get a better look than trying to do it with an Exacto knife.!!! I recently posted on this very issue.. Check it out.. But here's the Amazon link for the tool Its $9 and you can use it on your next builds. https://www.amazon.com/gp/product/B000F3SI2O/ref=ppx\_yo\_dt\_b\_search\_asin\_title?ie=UTF8&psc=1
You would just need to use a countersink bit to make the screws sit flush or a little bit into the fan.
https://www.amazon.com/Bosch-CST1-Titanium-Coated-Countersink/dp/B000F3SI2O