I've had blocks my entire life. It's my main form of stutter. Over the years I've found that the most effective strategy was to make a sound before you start a sentence. Like a quiet hum or even another work that you don't get blocks on. I find the word "so" very easy to say, so I try to start a sentence with that whenever possible. It can be quite mentally tiring thinking of how I can manipulate the start of a sentence so that I don't have a block. My advice - find what sounds you struggle with and make sure you don't start sentences with them! And if you do need to start a sentence with one of those sounds, add another easier sound or word before it.