See how your pup is laying in your avatar? That is a settled position. The other way that that they sometimes lay -- I know I'm not going to do a good job describing it -- but it's where they basically have their legs tucked under them -- makes it very easy for them to pop up. When they are in the settled position, it just requires more effort for them.
Mine has a tendency, when I say down, to just tuck her legs underneath her. To teach her to settle, I woud say "settle" and then move a treat around to her side and that forced her to move into a settled position. Then I would say "good settle".
I haven't had much sleep and am probably not doing the best job explaining it. sorry ...
Sit on the floor with your dog. Lie him on his side and hold the paws that are closest to the floor. Keep your fore-arms on the dogs side but not applying pressure or much anyway. In an unemotional voice say "settle". Most pups will fight it. Just keep at it until he settles and relaxes. Then release him, say good settle and reward. It's excellent because if you can get them so they do this on command, you can manage some potentially out of control situations.
This is different than the settle I use -- I guess it's whatever you want it to be.* I've attached a picture of what I call settle.* Are you saying that for Miles it is when he is lying with one entire side (head to toe) touching the floor?* To me, settle is nothing more than a comfortable down/stay -- and I use it with the term "blanket" when I want her to go to a special spot (on her blanket) and stay there.
That's how they are having us do it in class, all the way down on one side. I just hope someday, if things get crazy at my house, I'll be able to tell him settle and he'll go lie down. Just to keep things sane.