LSE

LSE, also called L6E, short for Last Six Edges, is a the last step in the Roux speedsolving method that solves the M-slice centers and edges (UF, UB, DF, DB) together with UL and UR edges.

Edge Orientation

An edge-piece is correctly oriented if the U- or D-face colour is in the U- or D-face. In other words, in this case where we have the Yellow centre on the U-face and White on the D-face, an edge in the U-layer is correctly oriented if it is Yellow-up or White-up, and one in the D-layer is correct if it is Yellow-down or White-down. It is only possible for an even number of the 6 remaining edges to be incorrectly oriented. (None, 2, 4 or 6, obviously.) Therefore it is possible to infer the state of the invisible DB edge from the four U edges and the DF edge that you can see. In the diagrams for this step, we are looking at the U face, with F and R for perspective. The (possibly) incorrectly oriented pieces will be in grey, and the rest of the cube (all of which is now correct) in pink.

UL and UR edges

If the pieces for UL and UR (in this case the Y/G edge and the Y/B edge) are not in the same layer, adjust the U slice until they are diagonally opposite each other (i.e. at UF & DB or at UB & DF), then M' U2 M' to put them in the same layer. Use M2 to put the edges into the D-layer. Adjust U so that an M2 puts the edges between their matching corners, then adjust U again to complete this sub-step. Your L and R layers should now be solved.

Final permutation of M-slice

Largely intuitive. Uses a combination of M (M, M', M2) and U (U, U', U2) moves.