Add red wine vinegar, shallot, strawberries, strawberry preserves and honey to a blender pitcher; blend until smooth. With blender running, add olive oil in a steady stream; blend until emulsified. Season to taste with salt and pepper.
For the Salad:
Add spinach to a large salad bowl and drizzle with just enough dressing to coat lightly (see recipe note); gently toss to coat. Sprinkle dressed spinach evenly with strawberries, walnuts, and feta cheese; drizzle with desired amount of dressing and serve.
Notes
Dressing the spinach and toppings separately mean that the toppings don't end up on the bottom of the salad bowl. Take care not to overdress the spinach since you'll be drizzling the salad with dressing after you add the toppings.
This recipe makes ample dressing and you'll likely have some leftover. Enjoy within one week.