In a large bowl, add oil and vanilla (or flavoring of your choice) to the confectioners' sugar.
Add a few tablespoons of the water and stir the glaze with a spoon until combined, pressing clumps against the side of the bowl to break them up.
Add confectioners' sugar or water a little at a time as needed, until desired consistency is reached. Glaze should be thick and viscous, not easily pourable, while still remaining pliable.
Pipe onto cake and bang carefully on a countertop to let the glaze run down slowly.
