If their visual memory is strong enough, have them visualize the word in their mind, then write what they see. Others may need more help such as:
It may help to first ask them to write the word, then work only on the letters they miss. Have them write the word with the letters they missed in a different color.
Also seeing the configuration, or shape, of the word may help. They can color or cut around the word to see its shape.
Understanding spelling rules can be helpful. These children must depend on seeing the word or principle in their mind instead of relying on verbally memorizing letters in a sequence.
Mnemonic memory devices can be helpful. Making rhymes, looking for patterns, drawing pictures or making sentences with their spelling words, such as; The old bold king did sing. Anything which gives them a picture to connect the work to will aid their spelling.
The child needs to help make up whatever will help them to remember the word. It must be something that appeals to the child. The funnier the better.