Turn the whole top yellow.

OLL stands for Orientation of the Last Layer — making the entire top face yellow. You have the cross; the four corners may still show yellow on their sides instead of on top. One famous algorithm, repeated with the right starting angle, fixes every case.

1. 1Count corners that already show yellow on top: zero, one, or two (three is impossible — if you see it, a corner is twisted from a mis-scramble).
2. 2One yellow corner — the "fish". Turn U so that corner sits at the front-left, then run Sune. Often solves it in one; at most two rounds.
3. 3Zero or two — find a corner whose yellow sticker faces you (on the front, not the side). Hold that corner front-left, run Sune, and you'll land in a fish. Go to step 2.

Between rounds, only the top layer changes — the two solved layers are safe the whole time. That's the quiet beauty of last-layer algorithms: they scramble and unscramble the bottom mid-sequence, always finishing clean.