When using the sling shot with the letters, it should say the name of the letter in addition to the letter sound.
Or an option button to all low you to choose the voice to say the name of the letter, sound, or both.
An a option for which letters and how long they can play.
If it possible, I would let my preschoolers play the sling shot letter games for 20 min.

We are working on games to more formally focus on phonics that will do exactly as you suggest. Here in the Sling King game, the focus is on gaining faster fluency with letter shape recognition. The letter sounds are added to provide early exposure to the sounds, but not to formally teach them. It does take a very long time for most children to associate the sounds to the letters so spending more time earlier on is important