The cross directly on the bottom

Keep white on the bottom from the start. Each white edge goes under the center of its other color: the white-green edge under the green center, and so on.

A white edge can only be in three places: top, middle or bottom. For each, a short move brings it down, in 1 to 4 moves. Those are this lesson’s cases.

The move that saves the most time: before bringing an edge down, turn the bottom (D) to bring its spot right underneath. Bring it down, then put the bottom back.

Edges can be correct relative to each other before they’re under their centers: a single D at the end lines up the whole cross. No need to put the bottom back after each edge.

Stop looking for edges one by one during the solve. Before turning, find where all four are and choose the order: first the ones that go down in one or two moves. Plan two edges at first, then three, then the whole cross.

Remember: Any cross can be done in 8 moves or fewer, 6 on average. If yours takes 15, that’s several seconds lost before F2L even starts. The cross trainer shows the shortest one for each scramble, move by move.

The cases

• On top, white facing up: U' F2. The edge is on top, white facing up. Turn U to bring its color above the matching center (here green, at the front), then F2 brings it down.
• On top, white on the side: U' R' F R. The edge is on top but the white faces sideways. U' brings it to the right, R' takes it down to the middle, F places it at the front, and R puts back the right edge that R' moved. If the right spot is still empty, U' R' F is enough.
• In the middle, under its color: F. The edge is in the middle layer and its color (green) is already on the green face. A single quarter turn of that face brings it down: F or F' depending on the side.
• In the middle, white facing you: D R' D'. The white faces you and the green is on the orange face: R' would bring the edge down to the wrong spot. D first brings the green spot under the right face, R' drops the edge into it, then D' puts the bottom back.
• On the bottom, flipped: F' D R' D'. The edge is in its spot but the white faces you. F' brings it back up to the middle, and it’s the previous case: D R' D'.
• Misaligned cross: D'. All four edges are on the bottom and correct relative to each other, but not under their centers. A single turn of the bottom lines up the whole cross: no need to place them one by one.

Troubleshooting

I break an edge I already placed

Before turning a side face, check whether its bottom edge is already done. If so, turn the bottom first to move it out of the way, or undo the face right after (like the R in U' R' F R).

The colors don’t line up

Turn the bottom (D): if the edges are correct relative to each other, they all land under their centers. If just one is still wrong, bring it up (R2 for example), turn U to put it above its center, and bring it back down.

I don’t know which edge to start with

With the one that goes down in a single move, then the shortest of the others. The ones on the bottom but flipped come last: they cost 4 moves.