When you teach the letters to a child who is a preschooler you can also have fun.
For similar letters you just make one shape. First you can put the dots by yourself and then you can ask her/him to put the dots on the right place. During this activity you can ask and help her/him: "What letter is this?",
"When I put the dot here what letter becomes is this?",
"What letter is similar to this one?" (I say "What is the brother of this letter?"),
"Where must we put the letter to make this letter 'ba'?"
Without making a new shape, you can make fatter the "fa" and put one more dot and make it "kaf".
You can show two forms of "ha" by putting a line on the "circle ha".
You can show "lamalif" by putting "alif" and "lam" together.
Teaching the combination of the letters...
You can cut tails of the letters...
You can colour harakah...