How can we help profoundly deaf children to begin to read when they find it a challenge blending sounds?

Use a similar approach as you would with a non-verbal child.

Can they blend in their mind?
If you show them the graphemes c-a-t can they point to a picture of a cat?
Are you teaching the words alongside BSL or images as this would help?

Cued articulation is also a useful tool when teaching phonics.

Here are a couple of useful videos:

Here is a video of the signs.

This video will help with cued articulation to support the development of speech sounds.

Have a look at the image bank in the SEND area. There are images for each phase and GPC. Use these when you teach blending and to check understanding.

If this child can blend then they can read the books.

Again use questions to check understanding, for example:

Point to a word e.g. dog and ask them to show you it in the illustration.
Say a word and ask the child to point to it.