The ultimate solution is just to live with it. The little shards are occasionally sticking up at just the right angle to force a minor puncture. It's about the same as stepping on rose or blackberry thorns or on the thin point of a broken mussel shell on the beach. The pain is not severe, more of a sharp twinge. Sometimes it gets stuck and you have to pull it out. It bleeds somewhat, which is a good thing.

Once the foot soles are thickened from use, it really takes a lot to force a puncture and your reflexes evolve toward letting off pressure from the ground as soon as something sharp is felt. A resulting wound is usually thin and tiny, and seals/heals pretty quickly.

I had a glass puncture wound while running just a few weeks ago, but the one before that was sometime last year. This is on asphalt city walkways/bikeways that are very heavily frequented by the public throughout the week. So, I feel like it's pretty rare, even there. Maybe once every 200 to 300 miles of running on city sidewalks or trails.