Knowing how to spell properly is about more than just sounding words out. However it is still very important to practice spelling sound by sound. This may seem obvious but many dyslexic people do not do it enough. You want to get into the habit of spelling every word out as you write, even the easy ones.
No one can spell every word sound by sound:
English is an imperfect language and as such no one can totally rely on spelling sound by sound. This can be very confusing for dyslexic people and create insecurity when learning to spell.
Spelling sound by sound is massively flawed. For example the word ‘right’, imagine someone had never seen the word 'right' written down before. If you asked them to spell it sound by sound there is no way they could know it has ‘gh’ in the middle.
In order for a person to know how to spell the word ‘right’ correctly they need to memorise that it has ‘gh’ in it.
To give you another example the word 'sign'. If you had never seen this word written down there is no way you can know it has the letter ‘g’ in it.
The truth about spelling:
For any person, dyslexic or not, spelling is about both sounding words out and using your memory. You must practice spelling sound by sound, and use your memory for the weird bits.
To be a good speller:
In order to be a good speller you need to identify which parts of words you can spell sound by sound and which parts you need to memorise.
For example the word ‘system’, with this word the only unusual thing you need to remember is the letter ‘y’. The rest of the word you can simply spell sound by sound.
Another example is the word ‘magazine’, you can spell most of this word sound by sound until you get to the last three letters. Therefore you only need to memorise those last three.
Even with a lot of simple words like for example the word ‘while’, you still need to remember it has a silent ‘h'.
Conclusion:
The truth is that spelling is about both sounding words out and memorising the unusual bits. If you want to become a good speller you need to know when to spell sound by sound and when to use your memory.