An A4 size has exactly these dimensions: 297 mm long and 210 mm wide. Equivalent size in inches is 11.69" long and 8.27" wide. These dimensions are not so important, but the lenght-width ratio is. What is really special about an A4 is that the lenght-width ratio stays the same when you cut it in half, and again the same when you cut the half in half and so on. So with just an A4, you can make templates in different sizes that all fit together.
Lets start showing how to fold a simple diamond.
Take an A4 size paper.
Fold in half.
Fold every side again in half.
Take the upper corner of every side. Fold the point of the right corner exactly on the right side fold and the point of the left corner exactly on the left side fold. Make sure the upper middle is perfect. I hope the picture helps :-)
Next, take the lower left (or right if you prefer) corner and fold up. The left point should be very sharp (no folding over the point) and the lower left corner should align exactly like shown on the picture.
Same for the other side.
Turn. Tadaa! A perfect diamond template!
Here you see the different template sizes you get when you start with half an A4 size paper, and 1/4 of an A4 size paper.
From this diamond, we can move on: if you fold your diamond in half, you get a perfect 60° triangle.
And starting from your diamond, you can also make perfect hexagons by folding the right side point and left side point exactly to the middle.
And here you have a set of four perfect hexagons, that fit perfectly with the folded diamonds and triangles!
You can trace the templates on paper if you want to use them for paper piecing, or make plastic templates using them.
Next time I'll show how to fold a kite and a pentagon from an A4 size paper.