Extended Slot
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Extended slot refers to a slot and an adjacent edge of the F2L. Some methods which use this step include APB, Nautilus, and MI1. In those methods, the last slot and an adjacent edge from the D layer remain in the first two layers, leaving what is called Last Extended Slot (LXS). LXS was originally used in 2006 as part of the Nautilus method. However, it received more complete development in 2020 as part of the re-development of Nautilus, and again 2021 as part of APB. The extended slot term was named by Liam Highducheck.
Last Extended Slot Methods
There are many ways to finish a solve upon reaching the last extended slot state. This can be compared to the number of methods which solve the last slot and last layer.
- Last Extended Slot (LXS): Fully solves the extended slot then the user solves the last layer. This step can be performed intuitively or by using algorithms. If all edges are oriented there are 116 cases. If edges aren't oriented, there are 467.
- EO + D layer edge: Orients the remaining six edges while solving the edge that belongs in the D layer. In the Nautilus method, this would typically be EODF. In APB, it is either EODR or EODF.
- EOFE or FE: Orients the remaining six edges while solving the two F2L edges. Or, if all edges are already oriented, solves the F2L edges without needing to perform any orientation. This LXS finish was proposed by Vincent Trang.
- L5E: Solves one of the F2L pairs, the corners of the last layer, then the last five edges.
- 2GLL+1: One of the F2L pairs is solved while permuting the corners of the last layer, then the last layer and the remaining edge of the F2L is solved.
- CX: First, all corners are solved. Then the remaining edges are solved in any number of steps.
- Polar: One of the F2L pairs is placed while orienting the left and right side stickers of the last layer corners to face the left and right side. The edges may also be separated to the left and right side, creating a domino reduction state on the left and right side. Then all pieces are permuted.
- CLL+2: First an F2L pair is solved. Then the remaining four corners and any two edges are simultaneously solved. Finally, the solve is completed with the last three edges.
Double LXS
The step can be taken further by simultaneously solving two extended slots. If all of F2L is solved except for the DF and DR edge and the dFR corner edge pair, this can be viewed as a merged double extended slot. There are 800 algorithms to solve this in a single step. This group of pieces, F2L solved minus a 2x2x2 block, forms the primary shape of the MI1 method. Double LXS could also be used when the two extended slots aren't adjacent, such as dfL and dfR or dFr and dbR, at the cost of many more cases and more difficult recognition.
