Make and chill the sauce. In a saucepot over medium heat or the indirect heat side of a grill), add the blueberries, Sambal, ketchup, brown sugar, apple cider and tomatoes. Cook while mashing the berries and tomatoes, until everything is broken down and the liquid begins to thicken, about 10 minutes. Simmer on low to further reduce if desired. Taste and add salt only if you feel it is needed. Set aside or pour into a container and refrigerate or place in a cooler over ice if not using right away.
Prepare the kebabs. In a large bowl, combine chicken, scallions, onion powder, oregano, rosemary, garlic powder, cumin, thyme, salt and pepper, to taste. Form meat around 2 parallel skewers held about an inch apart, making 6 kebabs of an oblong sausage shape. Press to secure firmly on the skewers—the flatter the better.