Concave Square with Straight Sides I am currently attempting to recreate the new Xbox Series X console within Blender, but am stuck on the top of the console as shown here: 
The console has a very nice concave surface on the top while still keeping the edges square and flat.

I have attempted using proportional editing to no avail (exaggerated to show issue): 
The surfaces near the corners are completely flat and should be bending slightly.

The bool tool with a sphere yields curved sides.

What would be a good way of recreating this complex curve?
This can be accomplished by using proportional editing.


Add a cube.





Switch to edit mode (Tab) and subdivide it (F3 > Subdivide). Use an odd number of subdivisions in order to have a single vertex at the center of the cube face. Use a low number of subdivisions, e.g. 5.







Select that single vertex at the center and enable proportional editing (O) and set the falloff type to Sphere.





Move the vertex down on the z-axis (G + Z). If you're not using the default dimensions of the cube you may have to adjust the radius using the scroll wheel of your mouse. The outer edges of the cube shouldn't be within the radius of the proportional editing.