For parents whose children have trouble blending, Feenie's advice is good. It is very important to say sounds precisely, as she says. But, if you want your child to get it every time, choose single-syllable words that have the structure CVC to start off with. Then move on to CVCC, CCVC and then to longer words (CCCVC, 'scrap', for example).
If you use words that begin with continuants - sounds that you can hang on to for a long time ('f', 'l', 'm', 'n', 'r', 's', 'w', 'z') - and ask your child to say the sounds as you run your finger under the sounds in the word, you can hear the word. For example, if you run your finger under the sounds in 'sat' (sssssaaaaat), you can hear 'sat'. It's easy! And, there's no memory work involved because you can hear the word immediately. After that, try longer words like 'milk' ('mmmmmiiiiiiiiillllllllllk) and ou will hear 'milk'. Then try 'flag' (fffffllllllaaaaag). Blending like this is a piece of cake.
However, once your child has read the word successfully, get them to say the sounds again, this time separately, and read the word. If you then put down some lines, one for each sound, you can get the child to write the word, saying the sounds separately as they do and then reading back the word.
Try it! It works!