Preheat your oven to 400°F. Grab a 9x13 inch baking dish and spray the bottom and sides with olive oil.
Slice your butternut squash between 1/8 and 1/4 inch thick. Layer the squash on the bottom of the baking dish, over lapping slightly. Add 4 slices of prosciutto then a blanket of mozzarella cheese. Next layer, add the squash, then brush on the pesto and then the mozzarella. Last layer, add on the squash, prosciutto and then cheese. Sprinkle with grated parmesan, dried Italian herbs and spray with olive oil. Bake for 40-45 minutes. I had to cover mine for the last 20 minutes to prevent over browning.
Allow to cool 10 minutes then slice and top with chili pepper flakes to serve.
Notes
Notice I did not season with salt since the prosciutto is salty enough for this dish. If you leave out the prosciutto then I suggest seasoning the squash with salt.