How to best socialize scared kittens?

I have 2 kittens (about 4-5 months old) in foster currently. They were rescued from the streets young and went to a different foster home where they were not properly socialized to humans and hardly interacted with :(. They are friendly with other cats, come out to eat and will even play with toys with me. However, if I stand up they run away. If I get semi close with my hands during playing they run away. I can’t touch them at all. I had them crated for the first 1.5 weeks so that I could medicate them and was able to pet them when they were contained, they even purred a bit. But i did not want to keep them in the crate long term. My foster friend suggested putting them back into the crate until they are more friendly, but I’m wondering if there is a way to warm them up to me without that? I spend a lot of time in the room with them, talk to them, just lay on the couch in there, and I can tell they’re comfortable in the space and happy to run around etc but just specifically afraid of humans. I’m worried they’ll never get adopted at this rate, but I know cats take time. I do have calming spray, feliway diffuser, but I feel this isn’t helping the human issue, it may be making them more comfy in the room, but I still am ‘scary’. They def would not take a churu from me or anything like that. Any suggestions?

TLDR: foster kittens afraid of human contact, unsure how to warm them up to me without having to crate them again.