I have achieved minimalism! One zig-zag (or stair-step, really) piece of knitting that is joined to itself in 3 different ways:
1. Entrelac joins (pick up stitches from side edge, join side edge to live stitches.)
2. Sliding-loop join from Rick Mondragon.
So, you can knit a cube with only one piece and with no seams… well, no sewn seams. Grafting is sewing, I guess, but it’s pretty flexible.