A friend who was moving gave Randy one of those rainbow colored nylon wind socks and, looking at it, I thought, “Well now, Hazel, I think you can make one of those easy with your 12″ square loom!” and I was right. I only had a stock of the green grocery bags so it isn’t as colorful as you could make it with bright colored bags. I’m sure you have some of these saved. It took two bags to weave the square and part of another one to make the streamers.
Here’s a link on how to cut your bags into one long strip, no fooling around with loops.
How to cut your plarn in a long strip.

This gal is a lot more fussy about them than I was but you’ll get the idea. I also cut mine finer, about 3/4 to one inch wide as I wanted to keep it light. I had no trouble with it breaking. (You could also weave a few squares to use as place mats for your patio table while you’re at it.)
Once I cut my plarn, I just butterflied it and dropped it on the floor and wove from there. Weave your square. I used a bit of sock yarn to sew it into a tube, leaving a tail about a foot long which I then knotted to the opposite side of the tube. I used an overhand stitch and did not pull it tight so that I could pull the seam to lay flat. It is just stiff enough to hold it’s tube shape but if yours doesn’t you could use a bit of wire or stiff plastic around the mouth to hold it in a circle. I leave that up to you. I cut loops from another bag and used a larks head to tie them onto the bottom edge about every 4th loop. Then cut the loop to make two tails. That’s it. Hang it out and enjoy the gentle waving in the breeze.