When you first start hunting ducks it's HARD. Nobody is going to tell you where and even if they did the information is stale and could be false.
I've found a lot of duck spots and will say how I found a few.
Went hunting in the woods where it's 4 miles by 3 miles and wandered around looking. The first "timber hole" I found wasn't even a good hole but it had a log to sit on and I sat there all morning listening to people kill ducks "over there".
Around 9 or so I got tired of just sitting so I hid my decoys and gun and simply walked around. I kept bumping into hunters.
Finally I got way to the other end of the area and then it happened. I got about 300 mallards up off an old farm pond hidden in the woods. Ironic but I'd fell into that same pond on my very first duck hunt many years earlier with my dad. He said I'd walked right by the sign that said "deep water" lol It's thick timber. Could have missed the sign easily as it's like 50 years old and rusty as fuck.
Had a dog then so the next day I parked close, carried my gear and brought the dog to the pond in the timber (Oakwood Bottoms in Illinois) We slaughtered the mallards for three days and then it all froze up.
That's how you do it but it takes a day or two of struggling.