Grease a cookie sheet and preheat oven to 350 degrees (F).
Beat coconut oil, brown sugar, and vanilla until smooth.
Slowly add flour and pecans. Beat until smooth.
Roll spoon-size portions of dough into balls and slightly flatten.
Bake for 15 minutes. Cool on baking sheet for 5 minutes then remove to a wire rack and cool completely.
Use the lightly spoon and level method for measuring the flour. If the dough appears too dry and crumbly to roll into balls, mix in additional melted coconut oil to the dough, 2 teaspoons at a time, until dough is cohesive.
You can roll the warm cookies in confectioners' sugar, or sift the confectioners' sugar over the tops to garnish. I found non-melting confectioners' sugar worked the best (available on the King Arthur Flour website).