I've had to make friends with five different starving but scared strays in the garden who kept running off and I totally agree with Empress
made sure newcomers had everything they needed within sight of their chosen hiding place including treats.
Then I visited them every couple of hours, sitting still, reading aloud or talking to myself, not too close, facing side o & pretending not to notice if they looked out at me.
I found facing sideways and glancing out of the sides of my eyes was extremely important. Leave a sweaty t-shirt near the food so they associate your smell with something good would also help. Oh, and after a couple of days start with the slow blinking.