What style of fly works best for redfish on the flats?

The kind that will work for whatever situation you are in. Seriously that is a loaded question. Do you need a recommendation on putting together a whole fly box of different patterns for various situations for redfish?

I just need a few patterns for clear, 6-12 in. deep water during winter conditions, casting towards schooling redfish from about 50 feet away.

think about what they are feeding on.

baitfish, shrimp, and crabs right?

there are tons of fly patterns to wade through but some clousers,
and some shrimp flies will do the trick....

as far as sizes from about a 6-2/0 hooks i personaly like bigger patterns...

and have both weighted and not because you dont want to spook 'em,

and cast to the out side edges of the school to pick them off, and not in the middle because when you hook up the school might break apart...

best tides...

A good plan might be to hit the local shop, ask what the fish are biting and buy some right there. Supports the local fly shop and gets the real time patterns that are working.

At one time or another, I've caught reds on the following flies:

Clouser minnows, either chartreuse over white or tan over white. My favorites are "Foxy Clousers" tied with Arctic fox fur instead of bucktail.

Deer hair sliders, again in tan or chartreuse

Seaducers, orange, brown, chartreuse

Spoon flies

Small poppers in white, chartreuse, bronze, or red

Cypert Mylar Minnows in chartreuse or grey

That is kinda of an open-ended question. I grew up on the coast and fish it several times a year, since I live in Dallas now. I dont think that Red's will school in the winter. You will find then on the flats only in the rivers and up in the bayou's, at least in good numbers. For example, I fished this past weekend and I had to go into a river system, which had reefs and flats, but was not the flats that you would typically see in the bays. All the fish that I caught this weekend were all feeding on mullet. You wont find shrimp this time of the year in the bays so I wouldnt use them. Clouser minnow and crabs should be your best bet. On another note, ever Red had a really blue tail. From what I understand this means that they have been eating a lot of crustations. I might be wrong on that but that would be my suggestion, mullet imitations and crab patterns.

I caught several nice reds and specks on a large jighook fly I tied with no particular creature in mind to imitate but it has a lot of flash and has a lot of motion in the water, I am no expert but it worked for me. I used large dumbbell eyes to get the fly down quickly into the deeper channels where the fish are holding right now. Just use a fly you have confidence in is my best advice.