The southern flounder is an “ambush” predator. They do not actively pursue their food like the speckled trout and redfish. They will lay in ambush waiting for their prey to unsuspectingly swim over them or be carried past by the tidal currents.
To find flounder, you need to find good ambush points in the bays and estuaries that have a good supply of shrimp and small fish. Flounder will tend to lay along drop offs or bury themselves along sandy bottoms near drop offs. The most productive area will be a point or channel where tidal areas choke down and have good currents which are likely to concentrate and disorient small fish and shrimp.
A good cut or channel will be like a superhighway for flounder. A good point or drop off will be like a buffet for them. They will come up to obstacles like jetties or changes in bottom contour like oyster reefs in an area that is rich in food they will drop down to hide and lay in waiting.
Because of their feeding habits, if you find a flounder, fish hard because there are probably several more nearby. They tend to congregate in large numbers when they find good conditions. The peak time generally will be with a dropping tide as the prey is carried out of the grassy flats through the small cuts and channels.