To smooth out the flaps on a cube, start with
one existing cube, and six cards folded the same way as for the original cube. You’re
going to cover each side with one card. The flaps are never going to tuck under this;
they will always be in an open “staple” shape like this… like in a “U” shape.
They go on a side just like this. The way I like to remember it is that you orient this
card in the way that the flaps from this card are already facing, and then bring it over
to cover that gap. And then it slots right in, like that. Continue around the rest of
the sides. Once you’re slotting one a side that already covered, you may need to pry
up the existing card a little bit, or don’t press them all down until you’re ready to
close the whole thing up. This is more difficult with stiff cards like these. So, I’m leaving
these raised from the surface a little bit, and I will press them all down at the end.
(Rounded-corner cards are also much easier for this.) And then, squeeze them all down,
and now you have a smoothed out cube that is stronger and sturdier and, depending on
what you’re building, looks nicer than a plain cube.