Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:5599032.

Box in two parts that fit together, in the shape of an acorn.

With wall thicknesses of 0.8mm and a tolerance (space for interlocking) of 0.45mm.

Each part, prints, the side with the largest flat surface on the print bed. ( does not require any supports. )

In the event of a print bed adhesion problem, use a brim.

If you have any questions or criticisms, or if you want another version (dimensions, or wall thickness, or nesting tolerance), please leave a comment.

Happy printing.

Credits : ( image modified ) https://freesvg.org/acorn-1573573240