I work my dogs at Task farms. It is a 10 acre ranch with another 5-10 acres of a field next to it. Thankfully, the field has just been mowed. The field has dips and rises. Lately I have been taking 8 sheep to the field. I have one dog split the sheep into groups of 4. I then have that dog hide four sheep at each end of the field. Then I bring out another dog and walk to the far side of the field where they can't see either group of sheep.
Talk about having to LISTEN! My girls are good spotters. It really frustrates them when they can't see their sheep. They would like to run out any which way to find their sheep. TWEET. "Look back, come bye." They need to learn to flank "without" being able to see their sheep. Easier said than done.
I'm looking forward to trying this in the desert when I have some friends to hold the sheep. At Task farms they pretty much hold themselves by grazing and the fact that they are out of sight from each other. I really try to come up with as many new exercises I can think of to keep my dogs from getting bored. Nobody likes to do the same stuff every day.