Place sliced almonds in a dry skillet over medium heat and toast, stirring frequently, 2–4 minutes until fragrant; remove and cool.
Rinse and thoroughly dry baby spinach; spin in a salad spinner or pat dry with paper towels.
Hull the strawberries and slice in halves or quarters depending on size.
In a small bowl or jar combine olive oil, balsamic vinegar, honey, Dijon mustard, minced shallot (if using), salt and pepper; whisk or shake until emulsified.
Transfer spinach to a large serving bowl and scatter the strawberries over the top.
Crumble the feta cheese evenly over the greens.
Sprinkle the toasted almonds and, if desired, a few extra almond slivers for texture.
Drizzle the dressing over the salad just before serving to keep leaves crisp.
Gently toss with salad tongs until ingredients are evenly coated with dressing.
Taste and adjust seasoning with salt, pepper, or a squeeze of lemon; serve immediately.