I need a huge natural plateau to form but with a slope. There can be some variation, a few hills or even mountains here and there, but the ground needs to be mostly gently sloping north to south.
It needs to be a huge plateau preferably 1000-2000+ miles on a side. The greater the size and slope the better, this will be limited by physical restrictions on how high land can get and plausible mechanisms for formation.
Assume the starting point is similar to planet Earth but you have the ability to rearrange continents and propose any physically possible processes that might lead to such a situation. Modest changes to Earth's structure are permitted but it must remain human habitable.
What processes could form such a structure and how big might it reasonably be?