This is a simple inbox for holding standard 8.5x11 paper.  When you load it in the slicer, it will be standing upright vertically, and it will rest on the bed at a 45 degree angle.  This allows the inbox to be printed on small beds.

The inbox is too tall for my Ender 3 V2, but will work better for 3D printers that can print greater than 11".  For myself, I just shorted it in the slicer, which means it will have paper hanging off the edge, but still works.

This can be printed with no supports, and I recommend 100% infill.