Microplane lemon and orange/tangerine peel. Save for later.
Cut stalks off of fennel and reserve franz. Cut bulb in half through the root. Slice fennel thin (with a knife or mandoline).
Cut peel off the blood orange or tangerines (whatever you are using) and segment. Save segments for later.
Squeeze juice from what remains of the blood orange/tangerine into a bowl. Add sliced fennel, lemon juice, 3/4 tbsp olive oil, pinch of microplaned lemon and orange/tangerine peel, salt and pepper. Toss.
Dice avocado flesh into large chunks. Place avocado on your serving vessel. Place fennel mixture on top of avocado. Add orange/tangerine segments. Top with salt and fennel franz. Drizzle with remaining 1/4 tbsp olive oil.