What you need to get started:

Large round oranges or lemons
Cloves
Marking pen
Grooving tool

Let's get started:

With your marking pen make a design on the orange.
With the grooving tool follow your design on the orange to make a groove.
Place whole cloves in the groove putting them right next to each other.
When done with this step place the orange in a brown paper bag and let dry for 3 to 4 weeks.
Take them out of the bag and add a ribbon at the top if you want.
They should smell great for your holidays.