I have always kept my bait moving for flounder, whether it be a live mullet on a Carolina rig or a jig of some sort. I fish from shore and try and find an "edge", where flounder will lay to ambush prey as it swims by. This edge may be a subtle change in depth..a ledge perhaps. I walk my bait along this edge, which seems to e a good retrieve speed, and generally will find flounder willing to eat. I have used a DOA Baitbuster on the Carolina rig, bucktails, and even DOA shrimp using this technique. You should have an advantage of covering more water than I can in your kayak, which should increase your success at catching these fish.