I feel your pain! A lot of the lakes in my area are of this type, and I have a heck of a time finding anything like a consistent pattern.
Frenchman’s advice is sound. Where I’ve had success(and it’s limited), it’s been simply finding ANYTHING even remotely resembling “structure”. A bar or slight indent or point(neither that really qualify), a patch of gravel in an otherwise sandy bottom, etc. Stuff that would be the “spot on the spot” in a lake with more structure often ends up as THE structure. Like Frenchman said, a simple 1-2′ change near or with weeds can make a difference. Locally here, that transition from hard to soft bottom often plays in.
If you know they are in there(something I’m not always sure of on some of mine), keep looking, keep looking, keep looking. When you find one or two key areas or spots in one of those lakes, chances are they’ll continue to be consistent producers.
I always mean to spend more time on these waters in open water, GPS in hand so I can mark little things like a pocket in a weedbed, a sandy bottom that gives way to gravel or whatever…and every winter I wish I’d gotten it done.
Good luck, you’ll figure a few out eventually!