I'm not usually one to emphasise a tool, but from time to time a tool emerges that has affordances that are ridiculous to ignore, Squeebles Spelling is one of those. Digital tools like Squeebles can transform spelling practice by making traditional equivalents pale in comparison, for more on why, and examples of how you can use it effectively, see this post on the DLC blog.
One of the only issues with Squeebles is that the default settings focus more on memory than spelling, by showing the child the word, before they try to spell it. In order to hear it rather than see it, you will need to ask the kids to change the settings, using the guide below:
Select Players from the top of the screen, then Settings
Ask the kids to make their settings the same as the image below: