I don't even have words for how happy I am with the ABC Beginners Cards that Kate Hadfield and I created together. I've been wanting something like this to use with my students for the LONGEST time!
A while ago I purchased this movable letter set from Amazon: Magnetic Learning Letters - Lowercase. It's perfect for a multi-sensory, tactile spelling experience. I like it because the vowels are red, and all the letters are lower-case. (I think it's confusing for kids to work with a combination of upper and lower-case letters in instances like this.)
For this activity, I picked one picture card and set it on an empty file folder in front of my student. Then I would place a line of letters below the picture, the 3 letters needed for the word, and 3 or 4 extra letters so she'd actually have to choose which letter sounds she heard.
If she wasn't sure where to start, I've say the word slowly, then sound it out for her. With "vet" I'd say "I hear the sounds /v/ . . . /e/ . . . /t/. Which letter represents the /v/ sound?" Usually that was all it took for her to grab not just the v, but to make the connection to the e and t.