How do I get the Floating Selection to stop floating in GIMP?

At: Windows > Dockable Dialogs > Layers ...or by way of just pressing Ctrl-L, open the "Layers" dockable dialog. Therein right-click on the "Floating Selection" and pick "Anchor Layer" to flatten it down. Maybe you don't need to this, but it drives me crazy. In Googling against this stuff, I learned that the usual way to flatten layers is to right-click in any one layer and pick "Flatten Image" from the menu that appears. This trick will not work with the Floating Selection however and you have to take this other route.