In New Jersey the boating season typically kicks off in April, which is the perfect time for winter flounder. Flounder move into the rivers from the deep ocean around November to spawn. By March the females have dropped their eggs and move into the bays to feed, while the males stay in the rivers fertilizing the eggs. Females are usually larger than the males so in April fish the bays for the larger fish. The edge of any channel is a good bet during any tide, but catching winter flounder is about 90% technique, much different from most bottom feeding species.
The first thing to prepare for is your rod & reel outfit. I recommend an ultra-light spinner spooled with 4-LB test. Your rig should consist of 2 or 3 flounder hooks with a 12" leader tied on so that the hooks dangle about 8 to 10 inches from one another. When selecting the hooks to use try to buy pre-tied hooks ornamented with 2 beads, preferably one red and one yellow. These beads can be purchased separately if desired, and easily attached to the hook leaders by re-tying. You should use a fish finding sinker that slides up and down the line above the hooks. This is especially important to your success while anchored and chumming, allowing your rig to drift away from the boat, while the sinker stays at the bottom. This also allows you to use heavier sinkers on the ultra-light, because there will be no resistance on the rig when fishing. Also get some yellow electric tape or Tommy tape and wrap your sinker with it. Flounder are sight feeders and are attracted to almost anything moving on the bottom, as long as they can see it. The yellow will draw fish from a further distance than the plain sinker.
When Baiting your hook, mix up the baits as much as you can between clam strips and sea-worm segments. Sandworms will stay alive longer than bloodworms when cut up into pieces. The soft parts of the clam should also be used, as they tend to break up on the bottom, causing the keen eyed flounder to see the pieces and follow them to your hook.
To set up your chum-pot, anchor your boat along the edge of the channel and fill your chum pot with a frozen clam stick or mashed up creamed corn. If using corn, be sure that every kernel is mashed up. Flounder and other fish cannot digest the whole kernel. When using the chum-pot, drop it to the bottom on a small cord. Once it hits bottom, churn up the mud with it, pulling it up and down as fast as you can for a few minutes. Before you tie it up, pull it up so that it is not laying on the bottom, the water will pass through it easier and release your chum more effectively.
Another chumming method is to buy whole clams. Hold the clam in one hand over the water and smash the top shell with a Billy club or small bat. Turn the clam over and smash the other side. Toss the clam out of your hand and hit it one more time with the bat to spread it out before it hits the water. The clam pieces are sliced up by the cracked shells and will sink since they are still attached to the clam shell fragments.
Cast your ultra-light rig as far off the back of the boat as you can, and allow for the sinker to hit bottom in the chum slick. Now bounce your sinker up and down slowly to churn up the mud and attract attention to your bait. Allow for some line to drift out past the sliding sinker. Now reel in your line slowly while pulling your rod tip up. By casting far away and retrieving slowly you maximize your persuasion of fish in the slick. Once you feel a little nibble, set the hook. You will be surprised at the great fight the 13 to 18 inch female flounder will give you. This same technique works in rivers but the fish are normal males 11 to 14 inches.