In a cup or small bowl, mix together the cornstarch, and 1/4 cold water. Gently stir the cornstarch mixture into the blueberries so as not to mash the berries. Simmer gently until thick enough to coat the back of a metal spoon, 3 to 4 minutes. Remove from heat and stir in the almond extract and cinnamon. Thin sauce with water if it is too thick for your liking.