Pour gelatin onto a spoon as you pour it over an already-set layer. This will help keep the set layer from breaking up.
For a smaller version of this recipe, use 3-ounce boxes of gelatin and 1/3 cup vanilla yogurt for each yogurt layer; reduce the water by half. Layer in an 8-inch square (2-quart) glass baking dish.
You can make this salad a day ahead of time. Just cover with plastic wrap and keep it in the fridge.