Edge in a Wrong Slot — White on the Side
F2L A12 — Front up · edge in back-right slot, front back
The corner sits above the slot, the front colour on top and white facing front. The edge sits in back-right slot.
Algorithm
8 moves. Hold the cube with the cross on the bottom and the slot you are filling at the front-right. Heads up: this solution disturbs another slot on the way, so only use it while that slot is still empty.
Setup / recognition
Apply this scramble to a solved cube to reach the F2L A12 case so you can practise it on demand:
Advanced — a piece is stuck in the wrong slot. Category: Edge in a Wrong Slot — White on the Side.
About this case
F2L A12 is one of the F2L cases — the pairing step of CFOP, where a white corner and its matching middle-layer edge go into a slot together. The corner sits above the slot, the front colour on top and white facing front. The edge sits in back-right slot. Solve it and one of the four slots is done; four of these and the first two layers are finished, leaving only OLL and PLL.
Do not learn this as a flashcard before you understand it. Every F2L case reduces to hide the corner, set the edge, rejoin them — the algorithm above is just the fastest way to say that for this particular position.
Easy to confuse with
These cases place the pair almost identically — they are the ones you will misread under time pressure. Drill them together: