Ice top and sides smooth. Using toothpick, draw witch face on cake top.
Using Tip 4, pipe a ball shape for chin and pull out, tapering off the end as you gradually decrease pressure. Using Tip 2, outline and pipe in mouth, add dot teeth, eyes, and string eyebrows; add pull-out dot nose, dot wart. Shape chin and nose to a point with fingers dipped in cornstarch, if necessary.
Using Tip 4, add pull-out string hair. Add Tip 104 hat ruffle, Tip 47 band and Tip 2 buckle. Pipe Tip 4 bottom bead border.