You activate Slick Fielding (primary is C) to place him at Catcher in your DD lineup...then you go back and reactivate whichever archetype you like best...go back and enjoy your game using your favorite archetype in the C spot...if you remove him from lineup, you will have to redo this process
Watch this video: https://www.youtube.com/watch?v=kZCZlyud6Hk