The present work attempts at quantifying the effects of using slats on the inner part of a modern multi-MW rotor as a post-fix to increase power production. In the process of doing this, the main behavior of the underlying physics is illuminated using a simplified BEM approach, and the effect of the lift and drag forces on local and integral power production and thrust is shown in a clear way. Two different methods (a BEM based and a free wake lifting line method) for determining angles of attack and lift coefficients corresponding to a specific loading on the inner part of the rotor are shown, and the results are compared. For the design of the slats, a 2D CFD based optimization approach is shown, and the final results from the algorithm for four specific inner airfoil sections on
the multi-MW rotor is shown. Finally, the impact of the alteration of the airfoil section force characteristics are shown in the design point using both a BEM based and a free wake lifting line method, and BEM based results are used to asses the effects of the addition of the slats on the annual energy production.