Once your child gets the idea of words having sounds inside them can be connected in rhyme e.g. I sa a bear at the fair that had no hair or underwear, then they are ready and willing to match sounds to letters.
Make Letters Real
You have to make letters and words as real and tactile as possible. This will really help children to be able to fully grasp their usefulness, their usage and the subtle differences between them.
Flash cards with pictures and words on them are a good start but you need go further than this. You need to create a more 3-dimensional 'picture' for the children to fully embrace.
Shapes and Sounds
Your job is simply to try and help your child recognise the shapes and sounds of letters. How do you do that? Well, let's say that you do that in as many ways as possible.
Use their Senses
Remember, children who suffer dyslexia are able to learn better if they apply all their sense to the subject. Allow them to see, hear, touch, smell, taste, sense the letters and words.
Sculpt the Words
Help them to not only draw the letters but also sculpt them in the snow, in paint, in clay, in lipstick, in whatever substance will hold the shapes. Trace the shape of letters on their skin, with or without colour. They will be able to visualise or sense the letter in their own way, even if you don't know why.
Prepare to be lead
You need to start by leading them on this voyage of discovery and they need to be content or willing to join you. hopefully, at some time alomg the way they will take over the lead and you should slip back and let them take over control.