Hand feeding and daily ignoring :D
You're dealing with a prey animal, so right out the bat any attempts to move towards them get a retreat response. The only part of them at first that wants any part of you is the OMG FOOD! part, so when you do engage them, treat liberally.
Wandering around the yard doing things near them but not paying any attention to them - and using an unavailable posture, as if you have something you don't want to share should engage their interest once they've gotten used to just having you around doing stuff in the background - Till they are sure you're not going to do anything sudden. By this point they may already be investigating you and shadowing you looking to see if you've turned anything over that might be hiding something edible. I'll pull weeds and toss them any worms I find. Casually though. Surreptitious duck baiting. Haha.
I put the treats in the palm of my hand, fingers down, from a crouching position so they have to put their entire head over my fingers to get the treat. After a few days of this they may be willing to hang out and nibble your fingers. Once they're willing to do that, I start wiggling my fingers under their chins - chucking them under the chin a little while they are having treats - getting them used to my hands moving and seeing that as a source of good things. From there I got them slowly used to being petted different places.
I always try to end on a good note - if I've pushed the ducky comfort zone, I'll treat again in a way that makes them remember me as the nice lady, not the scary lady.
I also hang out for a bit after treats and stay squatty and low and let them investigate my shoes or my sweatshirt.
It took about three months to get them almost to lap duck stage after they decided I was okay, but that did take awhile. Admittedly I wasn't all that available to take the time till after thanksgiving, so before that, they saw me twice a day for feeds, let outs and put aways, but I didn't hang out and chat and head bob back at them or really try to interact. Starting early might get even better results. I think in a way, it took about till they fledged for them to even get past that purely reactive state of being. Everything was a threat and they seemed to have only fear and food about till they feathered.