Transition zones are always a good place to target. Whether it's a weed edge or transition from soft to hard bottom and usually the more abrupt the better. Beyond that, it's more of a forage factor. If the small fish, perch, etc. are sipping bugs out of the mud; that will attract larger predators. But there can be a lot of bugs in the rocks too as well as crayfish and other forage. If fish are chasing suspended forage like ciscoes or emeralds, the bottom is basically irrelevant other than looking for ambush points (sunken humps, etc.) or places that could bottle neck or concentrate forage such as points or edges.
I'd be inclined to try finding an abrupt drop-off to a flat and first focus on the edge of the drop-off regardless of bottom composition. And depending on where you are at on the lake, flooded timberlines. Good luck to you.
