I had a really hard time getting my buttons cut flush for my mintyPi build so I made a cutting jig that is sized to a #10 hobby blade. This guide will give you 2.5mm of button left over which, in my opinion, is perfect. I prefer shorter buttons and they feel great.
**CAUTION*** Please be very careful when handling sharp blades. This model is very very small (only 10mm wide) and if you're careless you can easily cut yourself. Please use this with caution or under the supervision of someone who is experienced using hobby blades.
Push Plastic PLA
If your extrusion multiplier is not dialed in properly you may have a hard time getting the button or the blade to fit properly.