Welcome the wonderful art of iris folding! It gets to be very addictive once you start. It gets its name from the papers "move" your eye toward the center of the finished piece. Iris folding utilizes different colors and prints to add stunning layers of detail.
To start your own iris folding project, you'll need strips of a light-weight paper cut into strips 3/4 inch wide. In some of my projects, I also use 1/2 inch-wide strips. Depending on the size of the pattern and project, you'll typically need your paper strips at least 12 inches long. You'll need a shape outline your pattern calls for, double-sided tape, and scissors.
Select your iris folding pattern (several are available at my online store for instant purchase and download) and then select your paper to cut into strips. Most patterns use between 2 and 4 different colors for the strips. Some patterns call for 6, but this is unusual. Once your strips are cut and you've cut out the pattern shape, fold the edge of strips of paper length-wise with the white side on the inside of the fold--you'll want about a third of the color showing on "top" of the white. Try to imagine folding the strips into thirds (like a legal-size document) and not folding that last third over; you've got it figured out! One secret I've learned is to apply double-sided tape under the fold--open the fold up and apply the tape and re-fold the paper. The paper will be thinner and will stay flattened; thus your finished project will also be thinner.
You will be creating the iris folding on the backside of the finished project--you get to hide the "mess" you'll make as you create! :) Apply a line of double-sided tape only around the shape opening without going into the opening. (If you go into the opening/center of the project with your tape, you'll end up with a very sticky finished project.) Take your first color of paper and carefully, without touching the sticky tape! line it up with the black line that outline the number 1 (or "A") on the pattern. The fold of paper strip lines up to the number line. You also want to make sure that the white side of the paper strip is facing you. Once you line up the strip, you'll cut the paper so it overhangs the shape outline approximately 1/8-1/4 inch on both sides. This is overhang is what the paper strip is attaching to with the tape.
Continue working the pattern by following the numbers; the numbers get bigger/higher as you work toward the center of the pattern. You'll need to apply more double-sided tape each time you go around a full "lap" in the pattern. Apply the tape gently on top of the layers of paper strips you just placed. Depending on the pattern, you'll alternate between colors every second, third, or fourth number. Patterns that "reset" at the "1 position" with a 5 (1 lap) can use either 2 or 4 different colors. If you're using only 2 colors, all your odd numbers are one color and all the even numbers are the second color. If you're using 4 colors, number 1, 5, 9, ..... are a first color, numbers 2, 6, 10, .... are a second color, numbers 3, 7, 11, .... are a third color, and number 4, 8, 12, ..... are the fourth color. If a pattern "resets" at the "1 position" with a 4, you're using three colors.
Once you've run out of numbers to cover with your paper strips, you've arrived at the center. Typically the center paper is something that is meaningful or compliments the colors used in the pattern. You need to gently apply double-sided tape to the last lap of paper strips and place the larger center paper over the opening. Depending on what your final project is, a greeting card or wall hanging or ornament, you will be placing a piece of paper covering all the paper "mess" on the working or backside of the project. Gently but thoroughly apply double-sided tape to the working backside and place a backing paper over it. And just like that you're finished!
A variety of patterns are available for download at my online store and my Etsy shop. Kits are also available in these locations which contain the pattern, instructions (similar to these), and the papers you'll need. Finally, there's also several videos demonstrating how to follow and create iris folding projects on my YouTube channel, Emily's Papercrafts.