Place the ground saffron in a bowl and pour the hot water over the top. Let this steep for 5 to 10 minutes, or until the water has turned to a deep orange hue.
For the new method
Place the ice cubes in a bowl and sprinkle the ground saffron over top of them. Then wait 30 to 40 minutes until all of the ice has melted and the remaining water has taken on a deep orange hue.
Notes
It is best to use the bloomed saffron immediately, however, you can also make it ahead of time and keep it in your fridge for up to a week.
Both of these methods will give you a 1/4 cup of bloomed saffron.