Slice oranges in half and squeeze juice into a bowl.
Using a spoon, scoop flesh and seeds of oranges into another bowl.
Thinly slice peel into long strips.
Fold a cheesecloth in half to create one thicker strip.
Place orange flesh in center of cheesecloth and then gather it into a pouch. Secure with butcher's twine.
Place juice, peel, and cheesecloth pouch into a medium saucepan. Add water, just barely covering all ingredients.
Cook for 30 minutes over medium-low heat until peels are tender and can be cut through with a spoon.
Turn off heat and remove pouch. Allow pouch to cool to room temperature.
Once pouch is cool, squeeze into pan to release juices.
Discard pouch. Return pan to high heat. Stir in sugar and bring to a boil.
Reduce heat to medium-low and cook for another 30 minutes. Place a plate in freezer while marmalade cooks.
After 30 minutes, mixture should be lightly simmering. Put a spoonful of marmalade on plate. Wait 30 seconds. Push spoon through mixture. If it wrinkles, marmalade is ready; if not, cook for another 5 minutes and test again.
Remove marmalade from heat and allow to cool to room temperature.
Once marmalade is at room temperature, pour into a jar with a lid to finish setting in the fridge.
To serve, toast bread and spread marmalade on while still warm.