I agree with Rosebud! Giving a child twelve sounds to be learnt individually and out of context is a terrible way to teach. Firstly, asking someone to associate one thing, in this case a letter, with another thing, a sound, is called in psychology 'paired associate learning' and it's hard even for adults to do. Secondly, twelve is far too many sound-spelling correspondences to give to a young child in one go!
Here's what I'd do: take three sounds in a three-sound word ('mat', say) making sure that the first sound is one that you can stretch out (Examples are 'f', 'l', 'm', 'n', 's', and so on). Write the three sounds separately on three squares of paper in lower case and make them a reasonable size. Now put them on a white board or a clean sheet of A4 paper. Now, towards the bottom of the (landscape) piece of paper/whiteboard, draw three lines that are about the same length as the squares of paper. Place the separate squares jumbled up and out of order at the top of the paper.
Next, running your finger slowly under the first line and moving towards the last line say to the child. I'm going to say the word 'mmmmmmaaaaat'. Listen carefully as I say 'mmmmmmaaaaaat'. All the while, your finger should be about where the sound corresponds to where it is in the word. Thus, you finger should be under the first line when you say 'mmmm'.
Make sure that you don't separate the sounds for the child so that you don't say 'mmmm' [gap] 'aaaaa' [gap] 't'. You need to say the whole word smoothly stretching out the sounds until you get to the 't', 'mmmaaaat'.
Now say to the child, "As I say the word 'mmmmaaaat', what sound can you hear when my finger is under this (the first) line?" Or, if your child understands the concepts first, second and third, simply say, 'What's the first sound you hear when my finger is under this line?"
When you say 'mmmmmmmat'. The child should say, "I can hear 'mmmm'". And you say, "That's right! You can hear 'm'. Which of these, indicating the three squares, is 'm'?"
The child may not know. If that is the case, you tell them. "This is 'm'". If they get it wrong and point to the 't', for example, you don't need to tell the child that they're wrong. Just say, pointing to the 'm', "This is 'm'".
Now ask the child to pull the sound-spelling down on to the first line and to say the sound 'm' again as they do.
Repeat this procedure for 'a'. So, with your finger under the second line, say to the child, "What sound can you hear when my finger is under this line when I say - and now you finger is under the 'm' and being drawn across the word as you stretch it out - 'maaaaaat', allowing your finger to linger under the 'a' as you stretch it out. If the child can't tell you. Tell them by saying, "You can hear 'a'". And repeat 'maaaat'.
Finally, you now say, "What's the last sound?" or "What sound can you hear when my finger is under this (the last) line when I say 'mat'?" And here you may need to emphasise the 't' by saying it a bit louder. Each time, the child should pull down the sound-spelling on to the line and say the sound as they do.
Now you've built the word, model for the child the sounds 'm' 'a' 't', 'mat', pointing with your finger as you do and drawing your finger across the three lines as you blend the sounds in the word. So, 'm' 'a' 't', 'mat'. Get the child to repeat this.
After that, you build on this knowledge by, say, building 'sat' and then 'sit', all the time introducing just one new sound-spelling correspondence. After about a week or two, your child should be really good at building three-sound words with five, six or seven sounds, depending on the child and on how much time you have to spend.
What also helps enormously is also asking the child to write the word after they've built it. Draw three lines for them and get them to copy and say each sound as they write it. When they've written and said each sound, they read it back again 'm' 'a' 't', 'mat'. This helps to establish in the child's memory the connection between the sound and the spelling.
This is a very thorough way of teaching children sound letter(spelling) correspondences and it gives excellent practice in segmenting and blending.
Good luck! 