A block, in my humble opinion, is mostly due to you not truly allowing yourself to stutter freely. The block then happens as a sort of panic response. I never allowed myself to stutter absolutely freely, because I hated the idea of people hearing me stutter and go, "br-br-br-br-b-b-b-br-br-br-bread." I couldn't bare the thought of people hearig me talk like that. When I got older, I decided to let go and allow myself to stutter totally freely without holding back. I first began with doing it around my wife, and immediately, no blocks. Stuttering, yes. But blocking - not at all. I then worked on simply allowing myself to stutter in front of others. And now, I hardly care if anybody hears me stutter. I can't remember the last time I seriously blocked like before. And also, because I'm more at peace with people hearing me stutter, I stutter way less. Good luck!