Creating a Low Polygon Object in Meshmixer

Import Sphere

Select All

Choose the Select tool and select the entire sphere (Cmd+A or Ctr+A)

Reduce the Sphere

Choose the Edit Tool, then Edit, then Reduce

Reduce the Sphere

Choose Triangle Budget for the target. Choose 20 for Tri Count and Accept.

Move the Vertices

Choose Sculpt Brushes and Move

Ensure Refinement is Off

Click and drag the corners to modify your design

Plane Cut

Edit, Plane cut to give the design a flat bottom plane. Move the cut to the desired location and then apply the cut.

Change the Dimensions

Analyze, Units/Dimensions

Change the Dimensions

Change the Z to a size of your choosing, then Export your design