Prepare many identical small stickers (we had little circles).
Write the letter on a card stock.
Show the child how to place the stickers right on the line (of the letter).
Using very small stickers like we did, may be a bit difficult for the child in the beginning, but this way he practices his pincer grip and fine motor skills.
When the letter is done, it's all covered with stickers, it's time to practice tracing the letter with the index finger (just like with Montessori sandpaper letters).