How to curve the edges of a plane? I've been looking around and i haven't quite found a way to do this yet without going through a lot of trouble.. I'm trying to curve a plane. To be clear,i'm not trying to do this: What is the fastest way to create a curved plane?

What i'm trying to do, is this:


What i want to do is put inward curves on all 4 edges, and possibly a curve on 'top' of the plane as well. I managed to get one inwards curve by using the Curve Modifier, but i haven't managed to get multiple curves at once by using this. also, it messes up the rest of the plane when i do that. So, is there a way to do this?

P.S. For anyone who wants to know, i'm trying to make a shadesail for a 3D house project. The last time i did a shadesail, I made it manually and it took AGES so i'm just trying to find a way around this problem. Thanks :)
Note: This is non destructive way to do such thing. You can always use
  Proportional Editing to directly model this shape.



Add a Plane and Subdivide it as much as you need/want.





Add Lattice and Scale it by 2.
Go to Lattice Data tab and set U: 3, V: 3, W: 1.





Add Lattice modifier to the Plane and choose Lattice as Object.





Go back to Lattice in Edit Mode, select needed vertices and Scale them down and also move center vertex on the Z axis.




Blend file: