Take a needle and punch it

I can't tell if it's a serious comment or not but in case it's serious: Why even buy a laptop? If you're paranoid enough to want to do this sort of thing to something you're paying over $1.5k for, have you realized the consequences of what other things a bad agent can do?

Your data, your files are more valuable to the NSA than your microphone. If they care about what you're saying, your house is already bugged.

What if you need it one day? You can remove tape from the web cam, but a needle is quite permanent.

I would think that the microphone is connected to the motherboard with a plug of some sort. So just open it up and disconnect that.

External mic I guess.