Modular cube from recursive four-sink base
This cube is made from six units, each of which is a recursive four-sink base modified for use as a module.
Each base is folded from 8×8 grid (where 6×6 would suffice for the plain base) and one part is folded back, folding rectangular flaps. At this stage units could be connected like the units in the Jackson cube, however I additionally squash-fold the sides to create additional triangular flaps which make the assembly much more stable.
Four-sink base and variants are widely known and often tessellated, the modification for use as a modular is my design.