If you have access to it, use deionized water for best results.
Start with about 5 to 7 g (1 to 1. 25 teaspoons) of salt, then add more as needed. Keep adding salt and stirring until the gel turns back to water. Use a glass stirring rod or stick for this.
The water level in the ice bath needs to reach the agar water level in the saucepan.