Here are the basic steps for 2-ply Plarn:
Flatten and smooth a plastic bag
Fold in half lengthwise
Fold in half lengthwise again
Cut off the bottom
Cut off the top loops
Now you have a folded rectangle
Cut into 1/2 or 1-in strips, depending upon the plastic’s strength.
If the bag is thin, cut larger, 1-in strips.
If the bag is strong, you can cut smaller, 1/2-in strips.
Click here to see Rachel Schell’s excellent tutorial
Once you’ve practiced a few times, you can stack several (about five, or whatever your scissors can handle) folded and cut them all at once.
Lather, rinse, repeat!
How to Make 2-ply Plarn, Speedy Style