How to train a working dog inside flanks

Starting to teach Birk to come between me and the stock for her inside flank To purchase Twisted X https://amzn.to/2DslU9s To purchase American Hats https://amzn.to/2qXooK2 To purchase Blue Buffalo dog food https://amzn.to/2OtY7fi To purchase rakes for use in training https://amzn.to/33qxwnT To purchase collar/leash https://amzn.to/33ti0Yl To purchase dog training book https://amzn.to/34qG9ju http://bit.ly/2svTQ2u