Start by washing the spinach leaves under cool running water, then gently dry them using a salad spinner or paper towels to ensure they remain crisp. Slice the strawberries and cucumbers into bite-sized pieces. If using red onion, thinly slice it and soak in cold water for about 10 minutes.

In a small mixing bowl, combine balsamic vinegar, olive oil, and honey or maple syrup, whisking until fully emulsified and smooth. Taste the dressing and season it with salt and pepper.

In a large mixing bowl, start with a layer of fresh spinach. Add the sliced strawberries, cucumbers, and drained red onion. Crumble feta cheese over the top and sprinkle walnuts for crunch.

Just before serving, drizzle the prepared balsamic dressing over the salad. Gently toss the salad to ensure all ingredients are evenly coated with dressing.

Transfer the tossed salad onto a serving platter or individual bowls. Garnish with extra walnuts or crumbled feta if desired. Keep dressing separate if preparing ahead to maintain freshness.