This began with a cube and an Extrusion with the Boolean on Minus on each axis to make a hollow cube. Next, we made one just inside of it. Then deleted the center portions with Extrusions with the Boolean on Minus. Then sketches were made in the middle of each side beam in perpendicular dimensions and joined them with bridge curves. We changed the color of the corners to help keep track of the transformations. To finish we used Sweep on the edges along the lines between the beams to make the twist. After making one Pattern Geometry was used to fill in the others.