I having been trying out this the other day, and it turned out better than imagined. Coffee with Orange Zest!
The orange has been sliced and dried in the oven.
If you want to dry the zest in the oven, keep the temperature quite low. 50 degrees Celsius is fine. There is no "set time" to allow this to dry, so keep checking. If you pull your tray out and it's still moist, then it's not ready.
You will want to be able to pick up pieces of the zest and be able to crumble it in your hands. From there you can simply grind manually or do it in a grinder. You will have the same effect, either way.
However you like your coffee, I hope you like these!