Is it possible to create a folder containing a single icon? I guess you could drag one icon onto another, then remove the second one, but is there a more "elegant" solution?
You describe the only way to achieve this.
Create a folder by dragging one app on top of another, then drag one of them out of the folder again. It doesn't get any simpler than that.
Press any app icon until all of your icons jiggle. Drag any icon on top of the one you want to keep in the folder. If you want to name the folder do it now (see the word FOLDER at the top of the screen > on the right edge of that bar tap the tiny X to delete the word FOLDER > type in the name of your choice). Push the Home button to stop the jiggling. Now again press any icon until they all the icons jiggle. Drag the icon you do NOT want to keep in the folder to somewhere else on the screen. Push the Home button. Now you should have a folder with whatever you named it, and only the one icon you want inside that folder. (If you want to name or rename the folder later, push any icon until all the icons jiggle. Tap the folder you want to name. Tap the bar where it has the name or it says FOLDER. Tap the tiny X on the right side of the bar. Type the name of your choice. Push the Home button to stop the jiggling.