At Level 6 Town Hall you’re able to build up to 125 Level 6 walls (2,000 hit points). To max level each Wall Segment you will need 121,200 Gold.
Example: Level 6 Town Hall Base Design
This level 6 base design had won 10 attacks in a row. Keep your Splash Towers in the center of your base. Put as many defensive structures as you can in separate cells, prioritizing the stronger ones. The Giant Bomb should be placed near a valuable building (i.e. storages) where mass numbers of enemies are more likely to gather (i.e. goblins, barbarians). Don't forget to max everything before going to Town Hall level 7.