Care to try this 3D visualization problem while staying at home?

First, the easy 2D version. Imagine a square with length a. At each corner, cut out a square of length b. Divide what remains into squares and rectangles.

Solution:
Join together the inner vertices of the cut out squares to create a square in the middle of length a – 2b. What remains will be 4 rectangles of lengths a and a – 2b.

Now start with a cube of length a, from which have been removed cubes of length b at the cube’s 8 vertices. Divide what remains into cubes and rectangular solids. I hope you will not find this too difficult, and that you will appreciate how nicely everything fits together.