Grab a piece of cardstock, a sharpie, a few jumbo craft sticks, and some tape. In about five minutes you'll have a speech warm-up that classroom teachers will thank you for.
Fold the cardstock to make a sleeve for the craft stick and tape together. For your initial sound warm-ups, position the sleeve to the left and write your initial phoneme on the end of the sleeve that you'll insert the stick into. Then write several word endings on the stick. As the child moves the stick back and forth they'll create several target words to practice and at the same time they're getting some phonics practice in as well.
For the final phonemes, position the sleeve to the right. Feel free to use the back of the same stick you just used for an initial phoneme. Write a word ending that ends with your target sound on the edge of the sleeve closest to the end in which the stick is placed. Then write several initial sounds that work with that ending to make a word. Now the child is practicing several words that end with your target sound and practicing word families at the same time.
It took me less than five minutes to make these. You could easily make a small set of these for each group you work with by taking just a few minutes before your session. Alternately, make them as a group project and send them home for practice. Children would have a lot of fun making these if you gave them several colors of papers and pens to choose from when making them.