You can try the pier. At times it is good - my experience is either on or off there.
The wall groin just before Johnson creek. One side is deep - fish the edge and down the sides of the drop off the end. Downstream side off ends of goins on the beach can be good too. Not near as far to walk.
Johnson creek can be good. Best spot I found is under the bridge and beside/behind piles. A couple creeklets on either side of it too.
Yak in the lagoon is good option too. The creek mouth and the oyster flat on parking side just as it widens from the creek mouth. Parking lot side is the deepest all the way down.
I've been to Hunting Island before and saw a guy fishing at the end of that little boardwalk that goes out to the creek in the marsh. (On the right side of the road if you are going to the pier.) Is this a good option? Best tide? Could I use a minnow trap there and catch minnows (assuming it is not stolen)?
I assume live shrimp and minnows for the trout under the bridge over Johnson Creek?
I have never caught a flounder. Is there a place at Hunting Island that gives me a chance? Live bait fished slowly over muddy bottom?
(Sorry for all these questions. I've done 99% of all of my fishing in freshwwater. Only get 1-2 chances a year to enjoy the low country. I want to be effective as possible.)
I haven't fished the creek at the end of the boardwalk. We stayed in the cabins (when they still existed) on the creek that empties the lagoon. But you won't have to worry about anyone stealing your minnow trap. If its anything like that creek, if you bait your trap with shrimp heads or fish carcass, you will fill your minnow trap with tons of mudminnows within 10-15 minutes. You could just wait there while you gather bait.
I would assume that the lagoon would offer up some good flounder fishing as well as trout. We never fished the lagoon much, but we did fairly well with flounder on the pier just dragging a mud minnow slowly along the bottom using a Kahle hook and a couple of split shots.