Wash the fennel well, ensuring any dust and dirt has been rinsed off the fronds.
Thickly slice the fennel bulb and cut the fronds away from the fennel bulb and set them aside.
Lightly crush the fennel seeds with the back of a knife to release their oils.
Place the fennel fronds, fennel slices, and fennel seeds into a large pitcher.
Add in the orange slices and arrange them evenly throughout the pitcher.
Pour in the cold water and steep for 4 hours or preferably overnight for stronger flavor. You can also "sun steep" this flavored water for just 4 hours by placing the pitcher in a sunny area of your kitchen.
Refrigerate until ready to serve. Serve strained in chilled glasses over ice.
Garnish with orange slices and fennel fronds if desired.