Optional prep step: For the best flavor, I like to roast the seeds on a baking sheet at 350 for about 5-8 minutes until fragrant and golden. This is optional but I find it really improves the flavor.
Grind the seeds- place the fennel, coriander and cumin seeds in a coffee grinder or use a mortar and pestle to create a fine powder.
Place this powder and the water in a small saucepan and bring to a boil. Simmer for 5 minutes until fragrant and remove from heat. Add cinnamon or ginger if using and stir. Let cool to warm before adding raw honey (if using). Note: some sources recommend letting the spices soak in the water for up to an hour before simmering, though I haven't noticed any extra benefit when I've done this personally.
Strain through a fine mesh metal strainer and drink immediately or pour over ice for a cool drink. Can also be made in big batches, cooled and kept in the refrigerator until ready to consume.
Can I use already ground spices? In theory, yes, though all original sources recommend using whole dried spices and using immediately before brewing.