Preheat oven to 400°F. On a rimmed baking sheet, toss fennel with a drizzle of olive oil and roast, stirring occasionally, until softened and lightly browned, about 12 minutes. Meanwhile, scatter almonds on another rimmed baking sheet and bake, tossing occasionally, until lightly toasted, about 5 minutes. Let fennel and almonds cool slightly.

Using an immersion blender, regular blender, or food processor, pulse roasted fennel with fennel fronds, garlic, and 1/2 cup olive oil until a puree forms. Add almonds and 1/4 olive oil and pulse until pureed. Add remaining 1/4 cup olive oil, season with salt, and pulse quickly to combine. Use right away or refrigerate for up to 3 days.