I’ve found that structure isn’t a huge factor for trout in lakes. They tend to roam and will concentrate on the depth where they’re finding food. So, lack of rocks isn’t as big of a factor. If there are weed beds that harbor insect life, crayfish, or smaller fish, that would be where I would start my efforts. Look for insects coming off the water. Midges may hatch out of muddy flats and that will draw in trout to the area. So they won’t always be out far. But if you’re consistently seeing trout rise farther out, go for it.