Place a small skillet over medium heat and add the sliced almonds. Toast for 8 to 10 minutes, stirring frequently, until they are golden brown and fragrant. Remove from the heat and let them cool completely.

In a large serving bowl, whisk together the extra virgin olive oil, fresh lemon juice, minced garlic, Dijon mustard, kosher salt, and black pepper. Stir until the dressing is well combined and slightly emulsified.

Add the thinly sliced cucumber and shaved fennel bulb to the bowl with the dressing. Toss thoroughly to ensure all the vegetables are evenly coated in the bright vinaigrette.

Chop about 2 tablespoons of the reserved fennel fronds and sprinkle them over the salad. Add the crumbled feta cheese and the cooled toasted almonds to the bowl.

Gently toss the salad one more time to distribute the cheese and nuts without breaking them up too much. Serve immediately as a refreshing side dish alongside grilled chicken, fish, or pita bread.