When I saw this activity I thought it was perfect, both for reinforcing shapes and for pre-writing skills. I think this helped M realize that you have to build a shape. We might do this again with letters and numbers.
Sticker Shape Tracing
Theme: Preschool Skills
Materials: Shapes page, stickers
How to: Have your child trace the outline of the shapes by placing stickers along the line. If they try to put the stickers anywhere on the page, explain that they have to place them on the lines only.
Source: Muffin Tin Mom