How to use Scale and Extrude together? I'm trying to create this shape. I don't understand how does it work. If I use E+S I can't get the faces forming the perimeter with an angle less than 90°?
This can be done with insetting the faces. First select the faces you want to extrude. Then hit I button to bring Inset operator. In the operator panel, thickness value changes the scale and depth value you changes the extrusion depth.