Remove the top of the butternut squash and cut the neck into thin slices. You can do this by hand or with a mandolin slicer. It is not necessary to remove the skins - with the skin on you get s slightly more rustic taste. For larger butternut squash, you might want to halve or even quarter your slices. You're the boss.
In a bowl, rub in the olive oil, making sure that all slices are coated.
Place on a baking sheet lined with baking paper or a silicone baking mat, making sure the slices do not overlap
Season with sea salt and scatter over the rosemary or thyme (or a bit of both). Sprinkle sparingly with cayenne pepper if you'd like a bit of heat. I also seasoned some with paprika, with tasted equally yummy.
Bake for ca 20-25 minutes until the crisps are hardened and browned. THis time will vary depending on how thin your slices are.
Enjoy on their own or with dips
I actually cut the rest of the squash into slices and baked them as well, after scooping the seeds out in the middle. My kids enjoyed them as "pumpkin wheels" - much more fun to eat than just as boring little squares.