Empty Insert for HSW

Remix of the empty 1x insert included here: https://www.printables.com/model/152592-honeycomb-storage-wall. I wanted to include this as part of a model, and I didn't want the chamfers or recess included on the original. The *Flat files cuts some features off of the bottom - this is done to provide a way to use this without requiring supports, assuming the insert and model share a common bottom plane.