Preheat oven to 350°F. Spread almonds on a sheet pan and bake until fragrant and toasty, 8-10 minutes. Transfer to a plate to cool. When cool, use a small bowl to gently crush. Turn up the oven to 425°F.
Meanwhile, toss carrots with olive oil, Aleppo pepper, a few good pinches of salt, and some pepper. Bake 25-30 minutes, until carrots are tender.
While carrots bake, bring a small saucepan of salted water to boil. Cook lentils until tender, about 12-15 minutes. Drain and set aside in a small bowl.
Wipe out the saucepan you cooked lentils in and melt butter over medium heat. Continue to cook until butter starts foaming, bubbling, then turns starts to golden brown and smell nutty, about 6 minutes. Use a heatproof spatula to scrape up browned bits from the bottom of the pot. Transfer to a heatproof bowl and immediately add crushed cumin and fennel seeds.
Whisk lemon juice, half the lemon zest, mustard, and honey into butter mixture. Add half the dressing to the bowl with lentils and season with salt and pepper.
Lay carrots and radicchio in a shallow bowl and spoon remaining dressing over. Spoon lentils over, letting some fall in between the leaves and carrots and others nestled inside the leaves. Top with herbs, remaining lemon zest, crushed almonds, and flaky sea salt. Serve with toast.