My advice would be to figure out what your articulators do when they make a K sound and practice it on its own for a bit. It may seem silly but blocking is not a core stuttering behavior. If you can't make the K sound, you are doing something else with your articulators. Blocking is something we are do, even when we don't feel we have control over it. You'll need to baby step your way to  trying to replace what your articulators are doing when they block (tensing, locking vocal cords, pushing, etc) with what they do to make a K sound. Then you'll be able to worry about the vowel. That's where I struggle.