Prep your fennel by removing the bottom of the bulb and the fronds. Pull the outer layers off, and then slice thinly.
Cut the skin off the orange and slice the sections out. Save the remaining orange for the vinaigrette.
For the vinaigrette
Squeeze the remaining orange into a bowl.
Squeeze half a lemon
Stream in olive oil (roughly 2 tbsp)
Salt and pepper to taste.