Locating Flood Tide Flats
Some quick Tips
Online maps are your friend:
Look for flats off islands in the marsh as these typically have higher and harder ground around them
Lighter, sandier, soil flats also show up as lighter colored on their maps and typically have harder ground
Look for flats next to main rivers/larger bodies of water, these seem to hold the most fish.
Look for flats that have multiple drains onto them as these will serve as access points for the fish.
Look for food - Ultimately the fish are there to eat, is your flat holding crabs? Do you see crabs or their holes?
Don't write off small areas, some of my most consistent areas can be pretty small flats between two islands in the marsh.
The best way I have found to determine if a flat has fish is not to pole around it looking for them but get there as the tide starts to come in, stand on the poling platform, and just watch. If they are there you will see them pushing in.
Also some areas produce better in different times of the year. For example, during summer most of the areas I look for are by inlets or deep water while Spring and Fall flats I often target are further up river.