These activities can be completed initially by using the letter cards in your child’s sound pot, and then, writing them on paper / white board. Using the cards first allows your child to physically move sounds in and out of words. This reinforces that it is very important to use the right sound in the right place to make the right word.
If your child is going to make a mistake, let them. Then ask them to check it by ‘saying the sounds and reading the word’. They can then plainly see where they have gone wrong. If you intervene too soon, they will not compute the error or remember the mistake they were going to make.