Creating surface for contour

Hey,
just wondering how i would create a surface that slops inwards from all 4 sides (like the image) but in surface form so that i could contour the surface later on. Thanks!

Hello - a Loft between two rectangles seems like it might be what you need.

@freerhino273 - example attached
TaperedSquare.3dm (52.3 KB)

-Pascal