Practice and repetition is the secret code for competent reading. Well, sounding out the words is actually the application of the current letter-sound relationship knowledge. You cannot expect the child to decode the words over a short period. It is a gradual process, and you must be patient and persistent.
Here are Some Helpful Tips on Sounding the Words Out
Decoding the Words
You can help your child learn how to sound out the words they come across for the first time by teaching them to break the words apart. Teach the child to identify the phonemes. You can find phonemes charts online.
But the English language has several irregular conventions that can make sounding out words a bit of a hurdle. Take time with a child to learn different words together with their meanings.
Write the Words Down
Say the words slowly and stretch them out so that the child can understand. Hold the word and stop. You can tell them to repeat it, as well. Sounding out the letters in the order that they appear can eventually help the child blend the sounds and read several words. They can read thousands of regular words in this way.
The next step is to task the child to identify the letter and search for another one that matches the sound. The child needs to write the letter or a combination as soon as they recognize the sound.
When the child hears the word aloud, they begin to make the connection with spoken words. Read the words with your child and help them associate with printed letters. It is always a good idea to set aside some time to read some text as the child watches you identify each of the sounds with a finger. The child will do the same, and with practice, it will become easier.