Pair and store with U'
Step 1 / 5
Dw: 2 Bottom layers: turn 90°, front face goes right
The upper piece of the front right edge pairs with the lower piece of the front left edge. The top front edge is unpaired.
As in the beginner lesson, but turn U' instead of U. Then R' pulls the top front edge down without breaking a stored pair.
Step 1 of 5: Dw. 2 Bottom layers: turn 90°, front face goes right