Iris folding refers to a technique where folded strips of colored or patterned paper are layered in a spiral pattern behind an aperture. It is called Iris Folding because it resembles the iris of a camera.
There are several free iris folding templates on the Iris Folding Templates page.
Using a craft knife and template, cut out an aperture in the colored cardstock.
If you want to cut a fancy border, now is the time to do that too.
Position the card with the aperture cut-out over one of the iris folding templates, face down. You will be working on the back side of the card.
Tape the card to the template using non-permanent tape (Masking tape works well for this. If the tape is too sticky, stick it to a cotton cloth first to reduce its stickiness)
Arrange your folded strips of paper in the order that you want to apply them to the card.
Start with #1 on the template:
Using the next color, follow the same instructions for #2. Repeat all the way around the aperture, following the numbers and working inward as you complete each round. Stop when you have the desired size for the aperture opening.
The back of the card will look quite messy as you progress, but when you flip the card over it should look something like this.
To finish the center attach a piece of holographic paper, a small picture, a decorative button, etc. You can now mount your finished work using glue or double-sided tape. 3D Foam pads works well if you used a heavier weight paper for your design and you find that it is too thick to mount directly onto the card.