You will need:

Plastic Bag String, or plain yarn (I used standard plastic bags. You can learn how to crochet with plastic bags here)
Crochet Hook (I used size I. You can adjust as needed)
Tapestry Needle (the super cheap, big plastic kind)
Button (I used a cover-your-own so it would match)
Scissors

I used 9 bags for this project. The strips shown above are from just 4 bags.

The crochet stitches used are chain stitch, single crochet, and double crochet. A whip-stitch is also used.

Step 1: Making the Body

Row 1: Chain 21
Row 2-13: Chain 3, Double Crochet 20 (this will bring you to the end of the row)

Step 2: Making the Flap

Row 14: Chain 3, Double Crochet 20 (this will bring you to the end of the row)

Row 15: Single crochet in the second stitch of row 14 (don't chain up). Single Crochet in the next stitch. Double Crochet 7, Chain 1*, Double Crochet 7. Single Crochet 2. Put the needle in the top of the last stitch of row 14, and pull through.

Row 16: Double Crochet 4 stitches in the top of the last Double Crochet Stitch you did. (It should make a quarter circle) Double Crochet 13. Double Crochet 4 in the next stitch. Insert the needle in the base of the last row, then pull through.

To finish, I usually just pull the leftover strand through the loop, then pull it tight. Keep the leftover string to sew up the sides.

*The chain forms a button hole. You may need to substitute a chain for two or even three double crochets, depending on the size of your button. Just make sure they are centered in the row.

Step 3: Sewing the Sides

Using the tapestry needle, weave the string down to the base of the flap. Then line up the edges of the purse.

Whip-stitch down the sides. When you get to the end, tie off in a knot, trim the ends, then weave them in.

To sew down the other side, attach a loop to the base of the flap in the same manner you link them together.

Attach the button where you want it, and now you're done!

Step 4: All Done!

If you want, you can crochet a handle so you have an over-the-shoulder bag, not just a clutch.

Feel free to experiment with patterns made from different bag colors, or to change the size. If you change the size, just make sure the edges follow that pattern.

Enjoy your new, free bag!