I use Elkonin boxes to help my students hear discrete sounds. With my 1st & 3rd grade students I am working on short vowels. The Elkonin boxes are especially helpful when working with 2, 3, & 4 letter words. They can also be used to teach syllabication.
Also, check out my post regarding discreet vs. discrete sounds.
It’s a great resource. Check it out!
Here’s a handout that explains it: www.austinschools.org/curriculum/RtI/resources/document/reading/phon_awareness/Say_It_and_Move_It.pdf