bonito

Thought seriously about screed but quiet costly messy and drying time etc. Also no experience etc Thought easiest option using timber route

Looking for solid advice on laying 2x3 ? joists flat on a concrete base that is way out of level diagonally starting from high point gradually down across the room by approx 50 mm and gradually down the other end of room by approx 90mm. From high point secured every 12 inches ? With shims and packing blocks at the deepest drops. The highest point I intend to channel our enough concrete to lay flat the first few joists so top of joist is at the starting level. Need to do this so washing machine and dryers will fit under kitchen units. I intend to then lay chipboard flooring above. I'm a nutshell am I on the right track to keep this as simple but reliable as possible ? Hope my description makes sense Cheers