I can tell you what my Dad started out with on his first feedlot with cement bunks(200'). The bunks run North and South down my Dad's lane(already gravel), from the highway to his farmstead. There is a 16' gate at the very North end, of the bunks.

The bunks sit on a concrete pad, that is 4" higher, than the concrete for the cattle, with about 6" inward, for small calves to put their front feet on AND it creates a ledge to hold back manure AND the loader bucket or back blade can run against it, too(during clean-up).

Inside the lot, there is 10' wide x 216' long that is slightly sloped away from the bunks(guessing 3"-4" in that 10') BUT it also has a very slight slope from North to South (for liquid runoff)

Next, there is another 10' x 216' , that is sloped towards the bunks, that mates to that first 10' wide strip. This creates a slight "V" and worked really good for holding manure, but the liquids tend to run South, with that very slight overall slope (on the 216').

This really worked good as an initial start, He could drive the tractor/loader thru the 16' gate and get a lot of the manure hauled off on a regular basis.(little JD 3010 with loader)

Since those early years, he has added flat concrete, moving farther away the bunks, to the waterer.

I asked him once, if he wished he had made the first 20' wide section, totally flat verses "V" shaped. He said "Heck No" that works really well.