Step 5: Adding the Edges
Prepare the 20 edge parts as seen on the picture. Fold the flaps inside and sew along the edge, that the (nice) dotted twine-line is on the outside and the (ugly) thick line is on the inside.
Now you need 4 pairs and 4 trios.
I will begin with the trios. Sew them together as you did with the cube-covering - inverted (leather facing leather), fixing with staples, cutting the edge away, turn inside-out.
When you now lay the edge on the edge of the cube, you will notice that it looks kind of creepy, because it lacks of depth.
So take a bit of twine and sew the 3 parts a bit under the edges with 3 single knots together (Hard to describe, just take a look at the picture). This avoids that the edges are laying flat on the cube.
After you have finished the edge, take 3 styrofoam triangles and fix them on one of the 4 top edges with double-sided tape or glue. They will fill the edge and make them more fluffy.
Now you need to put a generous portion of glue on the inner side of the trio along the twine-line and fix it on the cube. Not all glues are suitable for holding leather together.
Same procedure with the pairs of edge-triangles. These go to the 4 bottom edges of the cube. On the bottom plate, they can be fixed with the strong stapler (see picture).
Now you can prepare the 12 center parts. First you have to sew the flaps on the inside, all around the shape, and then glue it to the right place. It is probably no surprise that the 4 halves go to the bottom edges of the cube.