I jumped on the bandwagon and made a whole bunch and gave them to friends and family. Most really liked them; some I'm not so sure. My grandma thought you would end up with popcorn. You won't. Although if you microwave it too long, you may hear a pop or two (I think it's just cracking), and if you nuke it way too long, it can burn and will stink up your house for days. Trust me on this one.
My friends and family may have since put them out for the squirrels and deer; I don't know. But we still use ours every winter. The kids love them and ask for their "beanies" every night. We warm them up and they take them to bed. I put mine under the covers to warm up the bed while I brush my teeth, etc, and then when I get in bed I keep it at my feet, which are always akin to icicles. The corn stays quite warm for a good 15-20 minutes.
At that time, I made the bags out of muslin...
...and also made an envelope-flap type cover to make it pretty. I added ribbon ties on some of them.
What I've found is that the cover didn't let enough of the heat come through, and we ended up just using the muslin bags. Of course, it was heavy decorator fabric, so something thinner might not be a problem.
If I were to do it again, I'd just make it out of flannel, with no extra cover. In fact, I will, just to show you how to do it. This is the finished product, so you can see what we're aiming for. I just used some rather ugly flannel that I already had. If you were making this for a gift, you would naturally want to use something cuter. I'm assuming.
You may have noticed the rice grains; I didn't have any feed corn on me, so I tried rice, which I know people also use. I thought about putting some dried navy beans in, but I've never heard of anyone using that, and I didn't want to end up with a bag full of refried beans or something. Now that I'm finished, I can tell you that I prefer the corn. I think it holds the heat better and it does smell a little popcorny. It's cheap; I don't remember exactly but it was something like $15 for 50lbs.
Okay, let's get started. First, cut 2 squares of fabric. I did them about 12"x12".
Now, put the squares right sides together, and sew a straight line across three sides, leaving one side open. I used the typical 5/8" seam allowance. I am a lazy seamstress, and did not iron the fabric, or pin it before I sewed.
Now, trim off the two bottom corners and then turn it right side out. Trimming the extra fabric helps to make a sharper corner when you turn it.
Next, you are going to sew two straight lines from bottom to almost the top, evenly spaced, to form three channels. I didn't take a good picture of that, but you can see what I mean in the photo of the finished one. Stop about an inch from the top (open) edge, and backstitch to finish the seam. I tried to show that below.
Now fill the three channels with equal amounts of corn. Don't stuff it absolutely full, you want some looseness for the corn to be able to shift around. If I recall, I think I used about 3/4 cup of corn in each channel. Next, take the open edge and fold it so the raw edges are inside. Go ahead and pin across that edge; it'll make the next step easier and will help keep the corn in. Hopefully the next 3 photos will help you figure out what I'm saying.
Now you've got it pinned across the top, as below.
Lastly, sew straight across the top. Be sure to cross the vertical seams that formed the channels so the corn will not shift from channel to channel. I ran a second seam across the top to reinforce it and make sure that all the raw edges were sewn in.
That's it! Done! It should look more or less (hopefully more) like the first photo. Now put it in the microwave for 1.5 to 2 minutes, and go cuddle!