• Start from M_RRmLvRmUvDUvRv and orient it as in the picture
• Close the two "ears" on top of the adjacent roof tile (call it A) obtaining a stack of three tiles
• Change both the hinging sides between the three stacked tiles and lower tile A
• The roof tile adjacent to A will be moved against a vertical tile
• This frees a flap to be turned 90 degrees into the final position