Hearing separate sounds in words is an important early reading skill. This skill can be taught even before letters of the alphabet are taught. Hearing separate sounds is words is called phonemic awareness. Phonemic awareness is part of a larger set of skills called phonological awareness.One way to teach a child to hear separate sounds in words is to use objects for each sound in a word. Sometimes it is hard for an adult to separate sounds in words. Here's a resource from The Reading Genie to help adults working with children learn to separate sounds in words themselves before attempting to teach it.
Try separating and blending sounds in words with objects.
You can help a child practice taking words apart by using toys or objects. You may want to use something edible like cereal or candy. Give as much support as necessary. First think of a word. Decide how many sounds it has. Line up that number of objects. Say a word such as cat. Have your child push forward one object for each sound in the word while saying each sound aloud.
Say /k/ and push an object forward,
say /a/ and push an object forward,
say /t/ and push an object forward.
You can work on blending sounds together also. Separating sounds is needed for spelling. Blending sounds is needed for reading. Say a word that you think your child with be able separate the sounds. Ask your child to show you the sounds in a word by putting an object out for each sound. Help if needed. Ask him to count the sounds. Then have your child touch or move each object as each sound is made. Then have him slide his finger under the objects and stretch and hold out the sounds as he blends them.
The word no would be an easy word to use to start. The letter n and o are continuous sounds.
Here are some videos of a child separating and blending sounds.