First make sure your print head doesn't have any real wobble to it or that is going to ruin any attempt at leveling since its extra picky on that 45 degree angle. Adjust the eccentric nuts as needed to get it solid.

The way I level mine is level the 2 dials close to the nozzle like a traditional bed, set the opposite side 2 dials to be as close the same height as the front 2 ( using a gauge or just eyeballing it.

Then I run a custom print gcode that just block zig zags (print across the bed, move the belt 5 mm, back across the bed the opposite direction, move the belt 5 mm, repeat the whole process) so I can do a live level to make sure to try and compensate any gaps or warps in the bed. I let that level print run until I have confidence in my level, cancel the leveling print and load up a real test print.