Heptominoes in a box

Puzzle description:
There are 108 different heptominoes, consisting of seven squares each. This is a generalisation of the classic pentominoes with much more and difficult problems.
The heptominoes can be divided in twelve subsets of nine heptominoes each. Every subset can be put together to a 8x8 square with a single hole always in the same position (see foto). This solution was found by Partick Hamlyn. So the heptominoes can be packed in twelve layers in a 8x8 box. More problems can be found at https://polyominoes.blogspot.com/search/label/heptominoes.

If you can read German: Mehr Informationen gibt es in https://welt-der-geduldspiele.blogspot.com/search?q=3D-Druck

Puzzle difficulty:
Packing the twelve layers (given in different colors as in the picture) is of medium difficulty because you know the twelve subsets. The problems for all heptominoes are hard to very hard.

Printing instructions:
The heptominoes come as 24 plates for 24 print jobs. If you print the two plates with the same number (i.e. plate4a and plate4b etc.) with the same color you get single color heptomino sets for each of the 8x8 squares. If a plate is too large for your printer you can separate the objects in your slicer.
A box is also provided.

The STL files for the heptominoes were generated using PuzzleCAD: https://www.thingiverse.com/thing:3198014. The PuzzleCAD file is also included.

Prints are fine with no supports.
I printed the puzzle in PLA at 0.2 mm layer height.