Concrete mix to screed patio

[silly_savage]

I have a concrete slab outside my house that previously had concrete slabs laid on a dry sand and cement mixer. Both of those have now been removed and I'd like to re-screed before laying foam underlay and artificial grass. My reason for this is the slab is very rough and it also pools water, I'd like to create a small drop towards the house where I'll install an ako drain between it and the house. My other option is to direct the gradient towards the garden and not have the drain.

I have a cement mixer, what's going to be the best mix to screed this slab?

I'd use leveling compound but obviously I don't want it completely level so I don't think that's the best choice.