When my Kinders are 'sound spelling' (using invented or developmental spelling), there are some sounds for which there is no single letter to use. When a student asks how to make one of these sounds, I pull out the corresponding card, use that moment to introduce the sound and its representation and then hang the card on the board for future reference. Over the years, I have found that having these tools available, makes for more fluent and independent sound spelling so my kiddos can get their thoughts out in writing!
Of course these representations of the sounds are not intended for reading instruction and I let my students know that there are other ways to make these sounds.
Print these pages on 8 1/2 x 11 paper or card stock , cut out and laminate to display those sounds that are difficult to guess when using invented spelling.
Please let me know if there you have suggestions for more sound cards that I could add to this list!