Preheat the oven to 350 degrees F (180 degrees C). Lay the Sliced Almonds (1/4 cup) in a single layer on a sheet pan. Bake for 6-8 minutes until lightly toasted. Set aside.
Trim the roots from the Brussels Sprouts (0.75 pound) and shred them. There's a lot of shredding in this slaw - for the ultimate ease - use the shredder attachment on your food processor. Otherwise, a box grater or mandoline work well.
Core and shred the Fennel Bulb (1/2).
Combine the shredded Brussels sprouts, Granny Smith Apple (1), Carrot (1) and fennel in a large bowl. Add a squeeze of Lemon Juice (to taste) and toss to combine.
In a small skillet, toast the Fennel Seeds (1 teaspoon) until warm, fragrant, and beginning to pop. Remove from heat and use a mortar and pestle, spice grinder or a heavy rolling pin to crush the seeds.
Transfer the fennel to a small bowl and add the Granulated Sugar (4 teaspoon) and Distilled White Vinegar (2 tablespoon). Stir until sugar is dissolved. Add the Mayonnaise (2 tablespoon) and stir to combine.
Add the mayonnaise mixture to the slaw and toss thoroughly to combine.
Just before serving, sprinkle with the almonds - if you add them too early, they'll get soft.