To get the 6th builder in Clash of Clans, upgrade your Builder Hall to Level 9. This action unlocks the B.O.B Control building, which is crucial for the 6th builder. Once you have the B.O.B Control building, complete its requirements.
Start by gearing up three buildings. Upgrade specific buildings like the Cannon, Archer Tower, and Mortar in both the Builder Base and Home Village. Next, choose a commonly used troop and upgrade it to level 18. Then, upgrade any defense to level 9, such as the Multi Mortar.
Another requirement is achieving a total level of 45 on Hero Machines. These include the Battle Copter and other Hero Machines. Once all these tasks are done, upgrade B.O.B Control to level 5.
After meeting all the requirements, you will get an unplaced B.O.B’s Hut. Place this hut in your Home Village to receive your sixth permanent builder. This ensures you unlock the 6th builder efficiently and effectively.