I use down and flat for Katie. Down is the legs in front, ready to go again, easy to get up from and flat is laid on her side. I used to use the 2 different words on my collie who I worked obedience with. I used to tell the dog down and then roll her onto her side saying 'flat'. I used to lay her like that for the down stay in obedience comps as it was more difficult for her to get up from that position. When I got Katie I automatically started to use the command and laying her on her side, and considering she's stubborn sometimes she got it pretty quickly, another way of teaching something like that is to wait till the dog does it natually and say the command although this may take longer for the dog to understand the actual command.