How do you get the 5th badge on Pokemon LeafGreen?

Answer 1

You'll have to wake Snorlax, and head down to Fuchsia City on cycling road.

This way, you will enter the city from the west. When you continue down the road, you'll eventually see the roof of the Gym.

Once inside, there'll be a maze, made up from nearly invisible walls. Go right, up and left to reach the back wall of the gym. There is the entrance of the maze, where you'll reach the Gym leader. The walls are slightly visible. Use Psychic or Ground type Pokémon to have the biggest advantage against this gym.