Cut one of the blood oranges in half. Set one half aside and squeeze the juice of the other half in a small mixing bowl. Add the rest of the dressing ingredients to that bowl and whisk vigorously until all ingredients are combined. You can set the dressing aside for now.
Cut your fennel bulb in half top to bottom and then slice one half with a mandolin (save the other half for another great recipe). If you do not have a mandolin, just slice with a knife as thin as possible. Set aside in a large mixing bowl.
Add 3 oz of arugula to the fennel, add 1/4 cup of the dressing and toss the arugula and fennel until all pieces are well coated. Set aside for now. Keep the extra dressing in case anyone needs more.
Take the 2/12 blood oranges you have left, cut the ends off and remove the peel, slicing one piece at a time, being careful to remove the pith but not the flesh. Slice into thin rounds; feel free to cut those into halves or quarters.
Lay your arugula and fennel out onto a serving platter or individual bowls. Layer with the blood orange slices, season with salt and pepper to taste, serve and enjoy!