After completing the three trials of the Akala Island captains, you search for Kahuna Olivia.
Go Through Diglett's Tunnel
Go south and Olivia will check your Z-Crystals. If you have cleared all three trials on Akala Island, Olivia will let you pass.
Go south and the path will split.
If you go east, you can battle Worker Frank. He has a level 22 Shieldon. You get 880 Pokédollars for winning.
East of Frank, there is a Dusk Ball.
Go west to return to the place where the path split, then keep going west. There is a hidden Escape Rope on some rocks along the path.
West of there, there are two rocks around the corner that you can check to get a hidden X Attack.
Go north past the stairs and use Tauros to break the rocks, then go west to get a Fire Stone.
Then go back to the stairs and go up. You will encounter two people from the Aether Foundation.
Go farther along the path and you find a Hyper Potion next to a wheelbarrow.
You can go south from the wheelbarrow to find a narrow passageway. Go through the passageway and you find some rustling sand around a rock. You can touch the rustling sand to battle a pokémon.
Continue along this path and you can battle Worker Jeff. He has two level 22 Digletts. You get 880 Pokédollars for winning.
From there, you can go east and jump down the one-way ledge.
Go southeast, then east past the wheelbarrow, and you can battle Worker Vaclav. He has a level 22 Archen. You get 880 Pokédollars for winning.
North of Vaclav, there is a hidden Nugget in the wooden crate.
Go south from there to find a couple of Team Skull Grunts. You will battle them both, with Hau helping you. The Grunts have a level 23 Ekans and a level 23 Salandit.
After the battle, Hau gives you a Max Ether.
Go south past where the Team Skull Grunts were. The exit goes to Route 9.
As you enter Route 9, you meet Looker. He gives you a Thunder Stone.
There is a police station at the start of Route 9, near where you saw Looker. Go into the station and talk to the police officer in the back to battle a Ditto. Try to catch it if you can, because it has good stat bonuses and a good Nature. After the battle, the other police officer gives you 12,000 Pokédollars. You can agree to help the police officer find other Ditto pretending to be humans. They are hiding in Konikoni City.
Go southwest from the police station and you can battle Police Officer Haruki. He has a level 24 Herdier. You get 960 Pokédollars for winning.
Go southwest from there and you will see a gate, but don't go through yet. Keep going southwest to a small beach. There is a hidden X Accuracy on the rock on the left.
To the east, you can battle Fisherman Mike. He has a level 23 Chinchou and a level 23 Tentacool. You get 736 Pokédollars for winning.
East of Fisherman Mike, there is a Net Ball.
Now go through the gate northwest of here to enter Konikoni City.