Wash the blueberries in a colander and remove all stems.Open the jello powder and sprinkle it over a rimmed baking sheet.Rinse the blueberries one more time (you want them wet) and then add the blueberries to the jello powder.Use a spoon to coat the blueberries in powder. Spread the blueberries out so that they are touching each other as little as possible. If they are touching, they will stay soggy and not get crunchy.Freeze or refrigerate the blueberries uncovered on the baking sheet for at least an hour. (You can serve these frozen or just very cold.)Serve immediately. If you put these in a bowl or in an dish where the berries are heaped together, they will get soggy. Still yummy, but not the same. It's best to serve them on a large platter or baking sheet.