The first is to take an 8 foot (2. 4 meters) by 8 foot (2. 4 meters) section of lawn out and dig down past the sod to undisturbed soil. Then fill the excavation with gravel and level. The second is to build a deck strong enough to support the weight of a hot tub filled with water and people enjoying themselves. You can use the plan below to construct a hot tub deck in one afternoon.