Do you need to teach them? Are you home educating? If you are not doing home ed then I would just focus on love of reading and read lots to them.
We moved country when my eldest was almost 5. He would have started school that September but we moved in the summer holidays and so he went to a sort of nursery here in this country (different language) for two full years and then school, as was standard for children his age. He was one of the older children in the year but it wasn't unusual.
In his English nursery, as he was in the year before reception, they had gone through the basic phonetic sounds of the alphabet, and I knew (from mumsnet!) that it was no longer correct to say "cuh, muh, buh" as we did when I was at school, but "kkkkh, mmmmmm, b-" (see alphablocks if that makes no sense). So of course I encouraged him when he pointed out letters on road signs, packaging etc.
I can't remember now whether he had learnt basic blending (which is joining the letter sounds together so C-A-T = cat) at nursery or whether I showed him this at home, but he found it easy and intuitive. Because he wanted to continue and we weren't at English school, I bought a set of the Julia Donaldson Songbirds and we went through 1-2 of them a night. I also made some games to play with sets of words which are phonically decodable with those sounds. Then as we worked through the books, we added different sounds like e as in me, ou as in round, sh as in fish, etc. And pretty much it was intuitive for him - there was a period where he became resistant to it and didn't want to try but then he picked it up again and he could read fluently by the age of 6, which was late by English standards but early for this country - everyone was surprised he could already read when he started school. I didn't teach him to read in the second language but he picked it up himself.
My second child is totally different. He can tell you what sound a letter should make but blending completely flummoxed him and he would just guess. I was puzzled by this because I expected it to be easy like my first child. A friend had passed on some reading activity books which she had finished with so I was reading through the teacher notes and I found out that there are basically several pre-reading skills which need to be in place before blending is even possible. The pre-reading skills are things like phonemic awareness and being able to break words down into individual parts. So for example, you can point out the concept of rhyming and play games relating to rhyming. Or simply read a lot of books with rhyming aspects or sing songs with rhymes so that they get the sense of the sound. The other end of this is looking at the beginning sound of words. Again, my eldest found that very easy but my second finds it very difficult. He can just about do it if you give the word with the first sound elongated and separated e.g. ggggggg-reen, b-read and then offer two options. "B-read, does it start with B- or Ssss?"
We think that he is probably dyslexic but they won't check until he starts school here which will be when he is just seven. In the meantime, we read to him and we point out rhymes and we do the easier starting sound questions.
Another way to help them break down words is to mark syllables e.g. clap "El-e-phant" "Rab-bit" - he can do that part.
Anyway what this has taught me is that in any skill, there is an underlying skill which needs to be in place first. A lot of the time due to the age that they typically teach something, the underlying skill is already in place so no need to explicitly "teach" it. But if it is not for some reason, then it can help to work on that. And if you want to support them in some future skill but they aren't there yet, you can sometimes find out what the "supporting step" of something is by reading about it. It's amazing!