Preheat the oven to 350 F. Spread pecans in a single layer on a baking sheet. Toast the pecans for about 5 or 10 minutes, watching the nuts carefully to make sure they don't burn.
Spread the prosciutto in a single layer on a separate baking sheet (or use a large single baking sheet for both prosciutto and pecans). Cook the prosciutto for about 10 minutes until crispy.
Core and slice yellow peaches.
In a large bowl, combine peaches, blueberries, and spinach.
Top with crispy prosciutto and toasted pecans.
Drizzle balsamic glaze (dressing) on top.