I would not till it, I would build raised beds with a layer of cardboard, newspaper, etc to kill the grass inside the beds. Leave the grass in between beds for paths.
Or go with a gradual takeover of the area with various trees, etc in true permie fashion, sculpt the area, again with grass-killing layer of paper, cardboard, etc (I have used old carpeting flipped over fuzzy side down) and just build beds on top with scrap wood , chips, compost, grass clippings (quit using chemicals!!), manure,spoiled straw, etc and plant away.
Basically that is what I have been doing to my gravel pit of a yard for the past 12 years. I have "framed" my plantings with the abundant big rocks, sifted the remainder to pebble and sand size (the sifting done with a milk crate and shaking), filling driveway potholes with the bullrock and gravel, then layering anything that will rot and make soil inside the beds. We have used cottonwood logs and branches for "framing" as well (makes lousy firewood).