One trigger finishes the white layer.

Cross done, white facing down. Four white corners remain, and one four-move sequence — the trigger you drilled in the notation lesson — places all of them.

1. 1Find a corner with a white sticker in the top layer. Read its other two colors — say white-green-red. Its home is between the green and red centers.
2. 2Turn U until that corner floats directly above its home slot, then rotate the whole cube so the slot sits at the front-right.
3. 3Repeat R U R' U'. Each round rotates the corner in place; after one, three, or five rounds it clicks in, white facing down. Pause after each round and look.
4. 4A white corner stuck in the bottom but in the wrong slot or twisted? One round of the trigger pops it back up to the top layer — then place it properly.

When all four corners are in, the entire white layer is solid and the side faces each show a solid bar across their bottom. That bar is your progress meter for the rest of the solve: if it ever breaks, undo what you just did.