First Tillie had to inspect the building materials.

Then I spent the day digging, mixing, cementing and measuring.  I even had to do a little trigonometry.  The base has to be perfect.

As I did this I ran a little experiment on some bits and pieces.  I let some computer fans whir away in the sunlight.  This will become part of the greenhouse heat sink.  Very geeky, but with green fingers.