Place an oven rack on the center shelf, and preheat the oven to 400 degrees Line a sheet pan with parchment paper or foil.
Using a sharp knife, carefully slice off the stem and bottom of the squash, creating flat sides (see photos). Place the bottom of the squash so it's flat against the cutting board, and cut the squash down the center lengthwise.
Use a spoon to scoop out and discard the seeds. Next, use a vegetable peeler (or your knifto peel away and discard the thick skin from each half.
Cut each half of the butternut squash crosswise. Cut into approximately 1-inch cubes, placing them in a large bowl as you go.
Add enough olive oil to coat the squash and toss to combine evenly. The squash should be glistening, but not swimming in oil.
Spread in a single layer on the prepared sheet pan. Sprinkle evenly with salt and pepper. Roast for about 20 minutes, then use a spatula to flip the squash so it caramelizes evenly on both sides. Cook for an additional 15-20 minutes, or until the squash is soft and caramelized, but not burned.
Let cool for a couple minutes, then serve. Store leftovers in an airtight container in the refrigerator for up to 4 days.
For the optional ingredients:
For ground cinnamon, sprinkle on a light coating when adding the salt and pepper. You could also try some nutmeg or a pumpkin pie spice blend
For fresh thyme, toss the leaves into the bowl with the olive oil and squash.
I would eye the quantities out; aim for 1/2 to 1 teaspoon of each.