One shape from my  pyramid pdf plans brought into rhino 

Copied and rotated to begin making the bottom of an object

Joined together to make the bottom outline

A copy scaled down and centred within the ouline. The smaller one dragged above the large one and a line drawn connecting to two

Used sweep rails 2 tool to make it solid

Another shape from my pdf opened in rhino

This is now stretched taller and extruded to give depth and 3 dimensional shape

planer caps filled and now we have an object. A seperate shape (rectangle) drawn and moved into the object