[freese]

Instant coffee is liquid, brewed coffee that then gets dehydrated.

1) grind the coffee 2) brew it however you like 3) cool the coffee from 90C --> cold 4) freeze the coffee 5) freeze dry for 24-48 hours

Fundamentally this will work but you're likely to run into a few problems. Your yield is going to be pretty low - one batch will likely get you ≈10-15 cups. Secondly, that coffee is really hygroscopic, meaning that it's so dry that it will absorb any moisture from the air. Unless you keep it in vacuum pouches it'll turn into a rock within days.