3x3x3 Box Packing Puzzle

The Slothouber-Graatsma puzzle: How to fit six 2x2x1 cuboid and three 1x1x1 cube into 3x3x3 container? Seems like no problem initially, but people who don't know the solution sometimes struggle.

Interesting things:

1. The small cube(s) can be omitted and the difficulty will be the same.
2. The 2x2x1 cuboids can be replaced by octagon prisms.
3. Try using fuzzy skin!