A tetraflexagon is a folded flat square of paper that has 6 different faces. Only two of the faces are visible at once, you have to fold & unfold to find the hidden faces.

Step 1: Fold Your Square Paper

You need a square sheet of paper. You will fold it in half vertically, then fold it in half again. Unfold it and you will see 4 columns. Now do the same folding horizontally, creating 4 rows. You will have 16 total squares folded into your paper. Cut out the middle four.

Step 2: Fold & Decorate

Now you need to fold your square frame into a tetraflexagon. Start with image 1;

Fold the left column over, on top of the frame
Fold the top row down, on top of the frame
Fold the right column over, on top of the frame

Next you need to fold the bottom section up while overlapping it with the previous sections, sort of like folding down a box lid. Watch the video to see how it's done. You take the right part of the bottom row and fold it up into place, then you have to turn the left part of the bottom row and turn it inside out (reverse the crease direction) so that it folds behind the square on top of it.

After your folding is done you can test out your tetraflexagon by folding it in half and opening the fold up to reveal a new face. You may hit a dead end, where nothing unfolds. If that happens just go back one step and choose a different direction. now you can decorate your tetraflexagon.