Preheat the oven to 350 °F (175 °C).
In a large bowl, mix the flour, baking soda, cinnamon, cloves, nutmeg, ginger, and salt. Set aside.
With an electric mixer, beat the sugar, oil, and molasses at medium speed for 1 minute.
Add the egg, and beat for 1 minute on low. Scrape the sides of the bowl and then beat for another minute.
Slowly add the dry ingredients and mix on medium for 2 minutes.
Add the crystallized ginger and mix until combined.
Roll each cookie into a 1 3/4-inch ball and flatten them slightly with your fingers.
Press each side of the cookie in sugar, which has been mixed with the orange zest, if using, and place them on a Silpat or a cookie sheet with parchment paper.
Bake for 13-15 minutes. As soon as they’re crackly, I take them out. If they’re not crackly, they’re not ready.
Cool the cookies on the sheets for 1 to 2 minutes, then transfer to wire racks to cool completely.
Keep in an airtight container for up to 5 days. They freeze great.